At first, Will, Tom and Oscar had the same amount of money. After Oscar spent some of his money, Will spent ³₇ of his money and Tom spent ²₃ of his money, Will had $110 more than Tom. In the end, the total amount of money the three boys had left was $531. How much money did Oscar spend?

	Will	Tom	Oscar	Total
Before	7x3 =  21 u	3x7 = 21 u	21 u
Change	- 3x3 = - 9 u	- 2x7 = - 14 u	- ?
After	4x3 = 12 u	1x7 = 7 u		$531

The amount that Will and Tom 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 Will had more than Tom in the end
= 12 u - 7 u
= 5 u

5 u = 110

1 u = 110 ÷ 5 = 22

Amount that Will and Tom had in the end
= 12 u + 7 u
= 19 u
= 19 x 22
= $418

Amount that Oscar had in the end
= 531 - 418
= $113

Amount that Oscar had at first
= 21 u
= 21 x 22
= $462

Amount that Oscar spent
= 462 - 113
= $349

Answer(s): $349