Expressions

Study Sheet

Expressions

Letters standing for numbers

Substituting a Value

Concept
The Big Idea

A letter holds a number we have not chosen yet. To evaluate, replace the letter with its value and follow the order of operations.

Example
Evaluating 3x+53x + 5 at x=4x = 4

Substitute: 3(4)+5=12+5=173(4) + 5 = 12 + 5 = 17.

In Plain Terms & More Examples

Concept
In plain terms

A letter stands for a number. To evaluate, swap in the value and follow the order of operations.

Example
Evaluating 2x+72x + 7 at x=5x = 5

Substitute: 2(5)+7=10+7=172(5) + 7 = 10 + 7 = 17.

Example
Evaluating 5a−35a - 3 at a=4a = 4

Substitute: 5(4)−3=20−3=175(4) - 3 = 20 - 3 = 17.