Calculate the number of grams of sugar (C12H22O11) that must be dissolved in 700 grams of water to prepare 20% sugar solution.

I know this is chemistry/math but Math Help Forum is the best, so I figured I'd ask it here. I can't solve this one for some reason.

I know that:

mass percent = grams of solute/grams of solution x 100

But I can't get it to work.Thanks for any and all help. :D