Vincent had $340 and Daniel had $130 at first. Each of them bought an identical blouse and an identical windbreaker from the same shop. The windbreaker cost 4 times as much as the blouse. In the end, Vincent had 3 times as much money as Daniel. What was the cost of the blouse?

	Vincent	Daniel	Difference
Before	$340	$130	$210
Change	- 1 blouse - 1 windbreaker	- 1 blouse - 1 windbreaker
After	3 u	1 u	2 u

Since Vincent and Daniel 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 = 340 - 130
2 u = 210

1 u = 210 ÷ 2 = 105

Amount that Daniel had in the end
= 1 u
= $105

Cost of 1 blouse and 1 windbreaker
= 130 - 1 u
= 130 - 105
= $25

The windbreaker cost 4 times as much as the blouse.

Cost of 1 blouse = 1 p
Cost of 1 windbreaker = 4 p

Total cost of 1 blouse and 1 windbreaker
= 1 p + 4 p
= 5 p

5 p = 25

1 p = 25 ÷ 5 = 5

Cost of the blouse
= 1 p
= $5

Answer(s): $5