No, it isn't!
first, the discount is 20 percent of 18 dollars, that is 18/5=3.6
this means that during the first week the prize is 18-3.6=14.4
now, the prize is marked up 20 % of 14.4! this is 2.88
so the prize later will be 14.4+2.88, that is 17.28, not 18
what is relevant here is what a number is a percent OF
If i understood it right when you estimate the quotient it help you have an idea
