How to Solve for ratios and proportions

In this tutorial the instructor shows how to solve ratios and proportions. He gives a two step approach to solve an equality of two fractions in which the value of a variable in unknown. He says that in the first step we should cross multiply the numbers across the diagonal. In the second step we need to divide and simplify to get the value of the unknown variable. This video gives a simple two step method on how to solve ratios and proportions.