What is a variable?

A variable is a letter, such as x or n, used to stand in for a number that is unknown or that can change. Variables let you write general rules and equations. Working out what number the variable must be is called solving for the variable.

Examples

• In x + 3 = 7, the variable x stands for 4.
• In the rule cost = 2 × n, n is a variable.
• A box or blank, like ☐ + 5 = 9, works as a variable too.

Quick facts

• The same letter always stands for the same value within one problem.
• Variables turn arithmetic into algebra.