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### Course: Algebra (all content)>Unit 1

Lesson 4: Evaluating expressions word problems

# Evaluating expressions review

An algebraic expression like 3x can be evaluated for any value of x. Say x=4, then 3x = 3*4 = 12. In this article, we review how to evaluate algebraic expressions.

## What does it mean to evaluate an algebraic expression?

An algebraic expression like $2x+3$ can be evaluated by substituting a value for $x$. For example, if $x=4$ then:
$\begin{array}{rl}& 2x+3\\ \\ =& 2\cdot 4+3\\ \\ =& 8+3\\ \\ =& 11\end{array}$
We can also evaluate more complicated expressions that have more than one variable. For example, we can evaluate $10+2p-3r$ when $p=4$ and $r=5$:
$\begin{array}{rl}& 10+2p-3r\\ \\ =& 10+2\cdot 4-3\cdot 5\\ \\ =& 10+8-15\\ \\ =& 3\end{array}$
Want to learn more about evaluating expressions? Check out this video. And here's a word problem video if you're curious how this concept might apply to the real world.

## Practice

Problem 1
Evaluate the expression $7+4b$ when $b=3$.

Want more practice like this? Check out this basic exercise and this more advanced exercise.

## Want to join the conversation?

• the last question was a little hard
(1 vote)
• I need help to do my exercice
• in an earlier video sal said that the orders of operations was “PEMDAS” was this not confusing to anyone else? all alone i though that it was “BEDMAS”
(1 vote)
• They mean the same thing. There are multiple acronyms used to help students remember the order of operations rules. The differences seem to be somewhat by country (where someone lives). Besides PEMDAS and BEDMAS, there are several others including BIDMAS, BODMAS, GEMS.

Here's how BEDMAS & PEMDAS line up together so you can see, there is no difference:

B=Brackets / P= Parentheses. Both refer to grouping symbols. You need to do the any work inside grouping symbols as your first step.

E=Exponents. Exponents are done as the 2nd step.

DM or MD = Multiply & Divide. These are in one rule/step. You need to do these operations from left to right.

AS = Add / Subtract. Again, these operations are done from left to right.

Hope this helps.
• This is so interesting,Idk why I didnt study these things properly in high school
• OK PLEASE give me something harder
(1 vote)
• How do i add whole number by decimals
(1 vote)
• you just add the whole number to the number before the point, and then you just add the decimal number behind the point.
(1 vote)
• 3x3x3x3x3x3/3x3x3x3 rewrite as 3 exponent n ?
(1 vote)
• No it would be 3 to the power of 6 and 3 to the power of 4
(1 vote)
• what does ^ mean
(1 vote)
• ^ means superscript or exponents
(1 vote)
• What is the perimeter of a square with a side length of \dfrac57
7
5
​ start fraction, 5, divided by, 7, end fraction units?
(1 vote)
• Perimeter means you need the distance around the outside edge of the square - add up all sides. Squares have 4 equal sides. And, your square has a side length of 5/7.
Perimeter = 5/7 + 5/7 + 5/7 + 5/7
or
Perimeter = 4 (5/7)

Hope this helps.
(1 vote)
• The expression 4x4x4, x gives the perimeter of a square with a side length of xxx units.
What is the perimeter of a square with a side length of \dfrac57
​7

​5
​​ start fraction, 5, divided by, 7, end fraction units?