How do we evauluate a variable expression?

In algebra letters can stand for numbers. When we substitute a specific value for each variable, and then perform the operations, it's called evaluating the expression.

Example evaluate the expression 3y + 2y when 5 = y.
1. Replace each letter with its assigned value.

The first step: 3(5) + 2(5)

(Use Parentheses!)
2. Perform the operations, to find the value of the expression.

The second step:

3(5) + 2(5) = 15 + 10 = 25