Will had $219 and Jeremy had $199 at first. Each of them bought an identical skirt and an identical windbreaker from the same shop. The windbreaker cost 2 times as much as the skirt. In the end, Will had 3 times as much money as Jeremy. What was the cost of the skirt?

	Will	Jeremy	Difference
Before	$219	$199	$20
Change	- 1 skirt - 1 windbreaker	- 1 skirt - 1 windbreaker
After	3 u	1 u	2 u

Since Will and Jeremy bought the same items, the difference  in their amounts remains the same.

Difference in the amounts that they had
= 3 u - 1 u
= 2 u

2 u = 219 - 199
2 u = 20

1 u = 20 ÷ 2 = 10

Amount that Jeremy had in the end
= 1 u
= $10

Cost of 1 skirt and 1 windbreaker
= 199 - 1 u
= 199 - 10
= $189

The windbreaker cost 2 times as much as the skirt.

Cost of 1 skirt = 1 p
Cost of 1 windbreaker = 2 p

Total cost of 1 skirt and 1 windbreaker
= 1 p + 2 p
= 3 p

3 p = 189

1 p = 189 ÷ 3 = 63

Cost of the skirt
= 1 p
= $63

Answer(s): $63