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## Class 6 math (India)

### Course: Class 6 math (India)>Unit 7

Lesson 2: Expressions with variables

# Evaluating expressions with two variables

Evaluating expressions with multiple variables involves substituting given values for each variable and simplifying the expression. By replacing variables with their corresponding values, we can easily compute the result of expressions, even for more complex examples with multiple terms and operations. Created by Sal Khan.

## Want to join the conversation?

• For the second expression, 3(2)-2+3(3)= 5 not 13
I thought you were suppose to add before you subtract?
• (1.) 3(2) - 2 + 3(3) (Multiply 3 by 2 and 3 by 3 because multiplication comes before addition or subtraction.)
(2.) 6 - 2 + 9 (Because we move from left to right, we subtract first.)
(3.) 4 + 9 = 13
• I thought PEMDAS is applied to Algebra? The last example that Sal gave made me confused. Can someone help me?
• MD (Multiplication and Division) and AS (Addition and Subtraction) go left to right. If a division problem comes before a multiplication problem, you do the division first.
• What does it mean when numbers are in parentheses?
• That means that you simply need to do the math inside those parentheses first.

Example:

2 + 3 * 5 = 2 + 15 = 17
(2 + 3) * 5 = 6 * 5 = 30
• When the equation comes to "6 - 2 + 9" would the answer not be minus 5? should you not add 9 and 2 and then subtract because of the order of operations ?
• This can be a common misunderstanding of the "order of operations" if you are using a mnemonic to remember them by. Multiplication and Division happen at the same time, not multiply first, then divide, and the same for addition and subtraction. You don't do all the adding and then do all the subtraction, you do them at once (unless there are brackets/parenthesis of course).

So in this case, it is
6 plus -2 plus 9 and you can put those in any order too
9 plus 6 plus -2 / -2 plus 9 plus 6 / -2 plus 6 plus 9 etc.
• Can somebody explain the PEMDAS
• P - Parenthesis
E - Exponents
M - Multiplication
D - Division
S - Subtraction

The order of which you solve an equation.
• can i write the dot which represent (x)times on any topic
• Yes, it is just another way of showing multiplication.
• pemdas is good for people
• However, it is better to write p e md as than pemdas, because this shows more clearly that multiplication & division are at the same level of priority, and addition & subtraction are at the same level of priority.

Have a blessed, wonderful day!
• I'm so confused. HOW are you deciding what numbers each of the letters are? How are you deciding the a=7, b=2, x=3 and y=2?
• ye hannah's right for random problems you can come up with random variables, the problems that people are determining true real life stuff like a rockets fins, you actually need to be precise.