it really depends on what X and Y stand for if they mean the same thing then of course but in the more likely case they would be totally different and would not be equal to each other
First you convert 20% into a decimal which is 0.2 and multiply that by 42 and you get 8.4, that's the discount. Then you subtract 8.4 from 42 and get $33.60 which is your answer. Hope this helps!!