# Variables

## Opening

# Variables

Equations and inequalities may contain one or more variables. When you substitute a value for a variable in an equation or inequality, the equation or inequality becomes either true or false.

Look at the balance scale in the interactive. It shows the expression *x* + 5 on the left and the expression 2*x* + 3 on the right.

- Substitute 5 for each
*x*in the expressions. What happens when*x*= 5?- Is the equation
*x*+ 5 = 2*x*+ 3 true? - Is the inequality
*x*+ 5 > 2*x*+ 3 true? - Is the inequality
*x*+ 5 < 2*x*+ 3 true?

- Is the equation

INTERACTIVE: Balance Scale X