Sean and John had $147 and $129 respectively. Each of them bought a cardigan and a jacket at the same price. The cost of the cardigan was 4 times as much as the jacket. In the end, Sean had 3 times as much money as John. What was the difference between the cost of the jacket and the cardigan?

	Sean	John	Difference
Before	$147	$129	$18
Change	- 5 p	- 5 p
After	3 u	1 u	2 u

Since Sean and John bought the same items at the same price, the difference in the amounts they had remains unchanged at first and in the end.

3 u - 1 u = 147 - 129
2 u = 18

1 u = 18 ÷ 2 = 9

Cost of 1 cardigan = 4 p
Cost of 1 jacket = 1 p

Total cost of 1 cardigan and 1 jacket
= 4 p + 1 p
= 5 p

5 p = 129 - 9
5 p = 120

1 p = 120 ÷ 5 = 24

Difference in the cost between the cardigan and the jacket
= 4 p - 1 p
= 3 p
= 3 x 24
= $72

Answer(s): $72