Variable

A variable is

    • usually denoted by a letter.
    • a quantity that may change within the context of a math problem.
    • also sometimes called an unknown.

Example:

2x + 3 = -5

The x is the variable. We can solve this and find that x = -4. In this case, x does not change. It's more appropriate to call it an unknown.

Example:

y = 2x + 3

In this situation, x and y are variables, meaning they can change. When you plug in something for x, it will change the value of y and vice versa.