#### Answer

variable

#### Work Step by Step

A variable is represented by a letter that may change within the context of a mathematical problem or experiment. Variables are always unknown and must be solved for; based on the context in which stated.
Commonly, a variable is representing the number we're trying to find.
Example: x + 4 = 10 ( x is the variable)
x +4 -4 = 10 -4 (subtract 4 from each side)
x = 6