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

Sometimes part of an equation is unknown.

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

To find the unknown number, the equation can be thought of as:

*2 times 5 equals some number.*

Since 2 times 5 equals 10, the unknown number is 10.

To find the unknown number, the equation can be thought of as:

*some number times 5 equals 20*.

Since 4 times 5 equals 20, the unknown number is 4.

Or, using the relationship between multiplication and division, the solution can be found by dividing 20 by 5.