At first, David, Henry and Simon had the same amount of money. After Simon spent some of his money, David spent ³₈ of his money and Henry spent ²₃ of his money, David had $189 more than Henry. In the end, the total amount of money the three boys had left was $721. How much money did Simon spend?

	David	Henry	Simon	Total
Before	8x3 =  24 u	3x8 = 24 u	24 u
Change	- 3x3 = - 9 u	- 2x8 = - 16 u	- ?
After	5x3 = 15 u	1x8 = 8 u		$721

The amount that David and Henry each had at first is the same.  Make the amount that they each had the same.  LCM of 8 and 3 is 24.

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

7 u = 189

1 u = 189 ÷ 7 = 27

Amount that David and Henry had in the end
= 15 u + 8 u
= 23 u
= 23 x 27
= $621

Amount that Simon had in the end
= 721 - 621
= $100

Amount that Simon had at first
= 24 u
= 24 x 27
= $648

Amount that Simon spent
= 648 - 100
= $548

Answer(s): $548