35% of a number is 17. Work out the number.

I think it is 48 but it is a really huge decimal.

Could you explain what I need to do?

Well first you would set up your ratio, 17/x = 35/100. You are trying to find x. To do so you cross multiply and divide. So first you have 17 * 100 which equals 1700. The you divide that number by 35 which is around 48 like you said. I usually just round to the hundredths place so just cut it at 48.57 but to be safe say approximately 48.57