An **equation** is a mathematical statement that two values are equal.

Equations are sometimes referred to as **number sentences**.

Equations are used to represent and solve problems.

Sometimes part of an equation is unknown.

Unknown values can be represented by a variety of letters and/or symbols.

Identify what operation is needed to solve for the total.

Twelve songs every hour for 18 hours is 18 groups of 12.

To solve for 18 groups of 12, use multiplication.

Identify what operation to use.

Since Sam sold 17 more memberships than Chris, subtract 17 from Sam's 43.