I really don't understand problem 1, could someone explain?? Why isn't it 0?

I'm going to assume you mean problem 1 in "let's practice" rather than the 1st problem in the video or just below the video. Problem 1 in practice is: (3/2)y-3+(5/3)z given the values of y=4 and z=3 Substitute the vales for the variables: (3/2)(4/1)-3+(5/3)(3/1) Follow PEMDAS rules. Multiply first. (3/2)(4/1)=12/2=6 (5/3)(3/1)=15/3=5 So, the expression is now: 6-3+5 Now, add and subtract from left to right. 6-3+5 = 3+5 = 8 The answer is 8. Why do you think it should be 0? Hope this helps.

You do this so that you can figure out how much of something there is when you have an unknown amount that can change.

Why is the answer to the second question 11? If I follow the order of operations shouldn't the answer be 5? Do addition first.. so 5 + 3 = 8.. then subtraction 13 - 8 = 5..

You aren't quite following order of operations. In PEMDAS, there are 4 steps, not 6. P = Parentheses: Do any work inside first E = Exponents: Do any exponents or radicals next MD = Multiply & Divide: These are one step. You need to work them from left to right AS = Add & Subtract: These are one step. Again, you need to work them from left to right So, when applied to the 2nd problem: 13-5+3 You go left to right: 13-5=8 Then 8+3=11 Hope this helps.

Wait, so, the first practice question has 3 over 2, isn't that an improper fraction? Am I supposed to treat it as an improper fraction and divide 3 into 2? Or, do I treat it as a normal fraction and try and figure out the problem? When I try to divide 3 into 2, i get 0.666... and so on. Thanks!

It's good that you saw that the answer 0.666... does not make good sense for the improper fraction 3 over 2. This should tell you that dividing 3 into 2 is an incorrect method. The fraction 3 over 2 actually means dividing 2 into 3. You should get 1.5 for the fraction 3 over 2. In general, the fraction a over b means dividing b *into* a, or equivalently dividing a *by* b. Have a blessed, wonderful day!

BEDMAS is an acronym like PEMDAS to help you remember the rules for order of operations. The rules don't change.

How is practice number 2 solved?

1) Replace each variable with its given value. 13-0.5(10)+6(1/2) 2) Follow order of operations rules (PEMDAS) -- Multiply: 13-5+3 -- Add & subtract: 13-5+3 = 8+3 = 11 Hope this helps.

How do i multiply 3/2 times 4

Change 4 into a fraction: 4/1 To multiply fractions, you multiply numerator to numerator and denominator to denominator. 3/2 * 4/1 = (3*4)/(2*1) = 12/2 Then, reduce the fraction to 6 Hope this helps. FYI - You may want to get more practice working with fractions. The lessons from here assume you know how to work with them.

Main content

Algebra 1

Course: Algebra 1 > Unit 1

Lesson 3: Substitution and evaluating expressions

Evaluating expressions with two variables: fractions & decimals

Google Classroom

We've already evaluated expressions with two variables. Now it's time to do it with fractions and decimals.

Khan Academy video wrapper

Evaluating expressions with two variables: fractions & decimalsSee video transcript

Let's study another example.

Evaluate start fraction, 1, divided by, 3, end fraction, a, minus, 1, minus, start fraction, 1, divided by, 2, end fraction, b when a, equals, 12 and b, equals, 6.

\begin{aligned} &\phantom{=}\dfrac13\blueD a-1-\dfrac12\goldD b \\\\ &= \dfrac13 \cdot \blueD {12}-1-\dfrac12 \cdot \goldD 6~~~~~~~~\text{Replace }\blueD{a} \text{ with } \blueD{12}\text{ and } \goldD b \text{ with } \goldD 6\text{.} \\\\ &=4 - 1 - 3 \\\\ &=0 \end{aligned}

Now, let's practice

Problem 1

Current

Evaluate start fraction, 3, divided by, 2, end fraction, y, minus, 3, plus, start fraction, 5, divided by, 3, end fraction, z when y, equals, 4 and z, equals, 3.

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Phong
Posted 4 years ago. Direct link to Phong's post “I really don't understand...”
I really don't understand problem 1, could someone explain??
Why isn't it 0?
Button navigates to signup pageComment on Phong's post “I really don't understand...”
(13 votes)
Answer
- Kim Seidel
  Posted 4 years ago. Direct link to Kim Seidel's post “I'm going to assume you m...”
  I'm going to assume you mean problem 1 in "let's practice" rather than the 1st problem in the video or just below the video.
  
  Problem 1 in practice is: (3/2)y-3+(5/3)z given the values of y=4 and z=3
  Substitute the vales for the variables:
  (3/2)(4/1)-3+(5/3)(3/1)
  Follow PEMDAS rules. Multiply first.
  (3/2)(4/1)=12/2=6
  (5/3)(3/1)=15/3=5
  So, the expression is now: 6-3+5
  Now, add and subtract from left to right.
  6-3+5 = 3+5 = 8
  
  The answer is 8. Why do you think it should be 0?
  Hope this helps.
  Comment on Kim Seidel's post “I'm going to assume you m...”
  (79 votes)
Steven C
Posted 4 years ago. Direct link to Steven C's post “Why is the answer to the ...”
Why is the answer to the second question 11? If I follow the order of operations shouldn't the answer be 5? Do addition first.. so 5 + 3 = 8.. then subtraction 13 - 8 = 5..
Button navigates to signup pageComment on Steven C's post “Why is the answer to the ...”
(7 votes)
Answer
- Kim Seidel
  Posted 4 years ago. Direct link to Kim Seidel's post “You aren't quite followin...”
  You aren't quite following order of operations. In PEMDAS, there are 4 steps, not 6.
  P = Parentheses: Do any work inside first
  E = Exponents: Do any exponents or radicals next
  MD = Multiply & Divide: These are one step. You need to work them from left to right
  AS = Add & Subtract: These are one step. Again, you need to work them from left to right
  So, when applied to the 2nd problem: 13-5+3
  You go left to right: 13-5=8
  Then 8+3=11
  
  Hope this helps.
  Comment on Kim Seidel's post “You aren't quite followin...”
  (59 votes)
Hector bencosme
Posted 13 days ago. Direct link to Hector bencosme's post “whos idea was it to add l...”
whos idea was it to add letters to math
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- IzzyJane
  Posted 16 hours ago. Direct link to IzzyJane's post “Life am I right”
  Life am I right
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dhruvajoshi
Posted 5 months ago. Direct link to dhruvajoshi's post “You guys really help peop...”
You guys really help people out when you help them with the problems.

Good job!
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bbautista1985
Posted 2 months ago. Direct link to bbautista1985's post “How do i multiply 3/2 tim...”
How do i multiply 3/2 times 4
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(2 votes)
Answer
- Kim Seidel
  Posted 2 months ago. Direct link to Kim Seidel's post “Change 4 into a fraction:...”
  Change 4 into a fraction: 4/1
  To multiply fractions, you multiply numerator to numerator and denominator to denominator.
  3/2 * 4/1 = (3*4)/(2*1) = 12/2
  Then, reduce the fraction to 6
  
  Hope this helps.
  FYI - You may want to get more practice working with fractions. The lessons from here assume you know how to work with them.
  Comment on Kim Seidel's post “Change 4 into a fraction:...”
  (17 votes)
abehrens28
Posted 25 days ago. Direct link to abehrens28's post “why do we do this?”
why do we do this?
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(9 votes)
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- MartN
  Posted 19 days ago. Direct link to MartN's post “You do this so that you c...”
  You do this so that you can figure out how much of something there is when you have an unknown amount that can change.
  Comment on MartN's post “You do this so that you c...”
  (4 votes)
Morgan Oesting
Posted 7 years ago. Direct link to Morgan Oesting's post “Wait, so, the first pract...”
Wait, so, the first practice question has 3 over 2, isn't that an improper fraction? Am I supposed to treat it as an improper fraction and divide 3 into 2? Or, do I treat it as a normal fraction and try and figure out the problem? When I try to divide 3 into 2, i get 0.666... and so on. Thanks!
Button navigates to signup pageComment on Morgan Oesting's post “Wait, so, the first pract...”
(6 votes)
Answer
- Ian Pulizzotto
  Posted 7 years ago. Direct link to Ian Pulizzotto's post “It's good that you saw th...”
  It's good that you saw that the answer 0.666... does not make good sense for the improper fraction 3 over 2. This should tell you that dividing 3 into 2 is an incorrect method.
  The fraction 3 over 2 actually means dividing 2 into 3. You should get 1.5 for the fraction 3 over 2.
  In general, the fraction a over b means dividing b into a, or equivalently dividing a by b.
  
  Have a blessed, wonderful day!
  Button navigates to signup page
  (7 votes)
🅻🅸🅶🅷🆃BENDER
Posted 4 months ago. Direct link to 🅻🅸🅶🅷🆃BENDER's post “How is practice number 2...”
How is practice number 2 solved?
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(3 votes)
Answer
- Kim Seidel
  Posted 4 months ago. Direct link to Kim Seidel's post “1) Replace each variable...”
  1) Replace each variable with its given value.
  13-0.5(10)+6(1/2)
  
  2) Follow order of operations rules (PEMDAS)
  -- Multiply: 13-5+3
  -- Add & subtract: 13-5+3 = 8+3 = 11
  
  Hope this helps.
  Comment on Kim Seidel's post “1) Replace each variable...”
  (13 votes)
Armani HATES MATH
Posted 4 years ago. Direct link to Armani HATES MATH's post “can somebody help me Eval...”
can somebody help me Evaluate 3/2 y - 3 +5/3 z when y=4 and z=3 like im just lost
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(6 votes)
Answer
- den.basmacioglu
  Posted 6 months ago. Direct link to den.basmacioglu's post “3/2y-3+5/3z y=4 z=3 3/2*4...”
  3/2y-3+5/3z y=4 z=3
  3/2*4/1-3+5/3*3/1
  12/2-3+15/3
  6-3+5=8
  ||I was thinking it is solved this way||
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  (1 vote)
Hildaliz T
Posted 3 months ago. Direct link to Hildaliz T's post “What's BEDMAS?”
What's BEDMAS?
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(4 votes)
Answer
- Kim Seidel
  Posted 3 months ago. Direct link to Kim Seidel's post “BEDMAS is an acronym like...”
  BEDMAS is an acronym like PEMDAS to help you remember the rules for order of operations. The rules don't change.
  Comment on Kim Seidel's post “BEDMAS is an acronym like...”
  (8 votes)