A defining variable is a symbol, such as x, used to describe any number. When a variable is used in a function, we know that it is not just one constant number, but that it can represent many numbers. Variables are instrumental in understanding problems relating to graphing. [1:52]

Percents can be rewritten as fractions, proportions, or decimals. We can use multiplication and division to find percentages or portions of different items. These methods are used often in money problems and other word problems. [1:34]