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# Variable

A variable is a symbol used to represent an unknown quantity. Often, variables represent fixed but unknown numbers. Variables are usually denoted with letters such as
In this case, is a variable in an equation. Solving this equation for will identify the value of that makes the equation true.
Alternatively, a variable can be used to represent a quantity that changes.
In this case, Izabella's weekly income could be different every week, depending on the number of hours she works. Therefore, the use of a variable is appropriate. Let be the hours that Izabella works in a week. Her income can be written by adding the fixed to the per hour.