First make the 62.4% as a decimal which is 0.624. Next you want to realize that the word "is" stands in place of an equal sign and the word "of" shows that you need to multiply. You can come up with the formula,
17.16 = 0.624x
and all you need to do is divide both sides by 0.624 and you get your answer.
x = 27.5
