Pamela buys a jacket, a windbreaker, a sweater and a blouse. The average cost of these items is $21. The total cost of the sweater and the blouse is ²₅ of the total cost of the jacket and the windbreaker. If the jacket costs $17.30 and the blouse costs $10.20, find the difference in cost between the windbreaker and the sweater.
Total cost of the 4 items
= 4 x 21
= $84

Total cost of the sweater and the blouse = 2 u
Total cost of the jacket and the windbreaker = 5 u

Total cost of the 4 items
= 2 u + 5 u
= 7 u

7 u = 84

1 u = 84 ÷ 7 = 12

Total cost of the sweater and the blouse
= 2 u
= 2 x 12
= $24

Cost of the sweater
= 24 - 10.20
= $13.80

Total cost of the jacket and the windbreaker
= 5 u
= 5 x 12
= $60

Cost of the windbreaker
= 60 - 17.30
= $42.70

Difference in cost between the windbreaker and the sweater
= 42.70 - 13.80
= $28.90

Answer(s): $28.90