Answer to Puzzle Contest:

$45.00. The best way to work problems like this is in reverse, and then checking your work by working them forward. In reverse:

X - 1/3X = 15
2/3X = 15
2X = 45
X = 22.5

Then:
2X = 22.5
X = 11.25

And finally:
X - 3/4X = 11.25
1/4X = 11.25
X = 45

Winner: FSteenberg