Any time you are solving a problem with percentages, use the formula below % = Is --- ---- 100 Of Percent over 100 = "is" over "of" In this case you are solving for percent and the "is" over "of" is $2 / $40 Then you cross multiply and divide. 100 x $2 = $200. 200 divided by 40 = 5. So the answer is 5