At first, David, Howard and Simon had the same amount of money. After Simon spent some of his money, David spent ²₇ of his money and Howard spent ²₃ of his money, David had $88 more than Howard. In the end, the total amount of money the three boys had left was $315. How much money did Simon spend?

	David	Howard	Simon	Total
Before	7x3 =  21 u	3x7 = 21 u	21 u
Change	- 2x3 = - 6 u	- 2x7 = - 14 u	- ?
After	5x3 = 15 u	1x7 = 7 u		$315

The amount that David and Howard each had at first is the same.  Make the amount that they each had the same.  LCM of 7 and 3 is 21.

Amount that David had more than Howard in the end
= 15 u - 7 u
= 8 u

8 u = 88

1 u = 88 ÷ 8 = 11

Amount that David and Howard had in the end
= 15 u + 7 u
= 22 u
= 22 x 11
= $242

Amount that Simon had in the end
= 315 - 242
= $73

Amount that Simon had at first
= 21 u
= 21 x 11
= $231

Amount that Simon spent
= 231 - 73
= $158

Answer(s): $158