This tutorial will show you how to perform you cross multiplication to solve for x.  You need to use distributive property and also solve for the equation.

In mathematics, the rule of three is the method of finding the fourth term of a mathematical proportion when the first three terms are known, that is, where the first term is in proportion to the second as the third is to the unknown fourth term.

To find the fourth term, multiply the second and third terms, then divide their product by the first term.

An equation is a mathematical statement, in symbols, that two things are the same (or equivalent). Equations are written with an equal sign. Equations are often used to state the equality of two expressions containing one or more variables.

Solving an equation means finding a value for the variable that makes the equation true.