The equation is part/whole = percent/100. Percent is unknown so it will be a variable, and it was marked down by 7 dollars so subtract : 25-7=18 now let's see our equation : 18/25 = x/100 Now solve : make sure 18/25 is simplified. (It all ready is) Now trade off : 18•100=25•x=1,800=25x (Divide by 25 on both sides and get) : 72=x. It was 72% off. Hoped I helped!