So you are saying that you want to start with 549, subtract some quantity "X" then take 10% of that (Y) to get 474.88 still?

Okay, taking X from 549 leaves 547- X and 10% of that is .10(547- X)= 54.7- X/10. So subtracting that from 547- X leaves 547- X- 54.7+ X/10= 492.3- (9/10)X= 474.88. To solve that subtract 474.88 and add (9/10)X from both sides to get (9/10)X= 492.3- 474.88= 17.42. Now multiply on both sides by 10/9: X= (17.42)(10/9)= 174.2/9= 19.35555... which you could round to X= $19.36. Y= (.10)X= $1.94.