A method of simplifying an equation in order to solve it for a particular variable or unknown, or in order to show it in a form having fewer fraction. Multiplying (or dividing) both sides of an equation by the same amount does not change the nature of equation - that is, the two sides are still equal. For example, x, y and w are known values in the following equation,

multiplying both sides by y will produce:

You can then find x by substituting the three known values. You can also express the original equation without fractions, by multiplying both sides by y and then by z:

In each of these examples, cross multiplication was used to change the appearance of the equation.