Julian had $339 and Henry had $139 at first. Each of them bought an identical skirt and an identical blouse from the same shop. The blouse cost 2 times as much as the skirt. In the end, Julian had 3 times as much money as Henry. What was the cost of the skirt?

	Julian	Henry	Difference
Before	$339	$139	$200
Change	- 1 skirt - 1 blouse	- 1 skirt - 1 blouse
After	3 u	1 u	2 u

Since Julian and Henry 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 = 339 - 139
2 u = 200

1 u = 200 ÷ 2 = 100

Amount that Henry had in the end
= 1 u
= $100

Cost of 1 skirt and 1 blouse
= 139 - 1 u
= 139 - 100
= $39

The blouse cost 2 times as much as the skirt.

Cost of 1 skirt = 1 p
Cost of 1 blouse = 2 p

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

3 p = 39

1 p = 39 ÷ 3 = 13

Cost of the skirt
= 1 p
= $13

Answer(s): $13