What if the paycheck for your summer job were represented by the algebraic expression
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CK12 Foundation: 0102s evaluate algebraic expressions
Guidance
When we are given an algebraic expression, one of the most common things we might have to do with it is evaluate it for some given value of the variable. The following example illustrates this process.
Example A
Let
Solution:
To find the solution, we substitute 12 for
Note: At this stage of the problem, we place the substituted value in parentheses. We do this to make the writtenout problem easier to follow, and to avoid mistakes. (If we didn’t use parentheses and also forgot to add a multiplication sign, we would end up turning
Example B
Let
Solution
Many expressions have more than one variable in them. For example, the formula for the perimeter of a rectangle in the introduction has two variables: length
Example C
The area of a trapezoid is given by the equation
Solution:
To find the solution to this problem, we simply take the values given for the variables
The area of the trapezoid is 100 square centimeters.
Watch this video for help with the Examples above.
CK12 Foundation: Evaluate Algebraic Expressions
Vocabulary
 When given an algebraic expression, one of the most common things we might have to do with it is evaluate it for some given value of the variable. We substitute the value in for the variable and simplify the expression.
Guided Practice
Let
Solution
Practice
Evaluate 18 using

2a+3b 
4c+d 
5ac−2b 
2ac−d 
3bd 
a−4b3c+2d 
1a+b 
abcd
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