Evaluating Expressions

• We substitute player for player in sports to give breaks. In order to substitute with the best outcome, you want to make sure they play the same position.

• It is the same thing with expressions. When we substitute, we will put in a number for the letter that it is equal to. The number and the letter are playing the same position.

• Example: If x=4, we can plug 4 in anywhere we see an x.

When you are given a number to plug in a variable's place, you are able to evaluate an expression.

Example 1: 3x; x=4; would give you 3(4), which equals 12.

Example 2: 3x+2y; x=5, y=4; so 3(5)+2(4)= 15+8=23

You MUST use the order of operations to evaluate correctly.

Please Excuse My Dear Aunt Sally (PEMDAS)

Parenthesis, Exponents, Multiply/Divide, Add/Subtract

*Be sure to write this at the top of every problem and check off each step as you go.

*Remember Multiply/Divide are whichever you see first left to right. This is the same for add/subtract.

Vocabulary Review