Olivia buys a sweater, a blouse, a windbreaker and a coat. The average cost of these items is $30. The total cost of the windbreaker and the coat is ³₅ of the total cost of the sweater and the blouse. If the sweater costs $17.30 and the coat costs $7.70, find the difference in cost between the blouse and the windbreaker.
Total cost of the 4 items
= 4 x 30
= $120

Total cost of the windbreaker and the coat = 3 u
Total cost of the sweater and the blouse = 5 u

Total cost of the 4 items
= 3 u + 5 u
= 8 u

8 u = 120

1 u = 120 ÷ 8 = 15

Total cost of the windbreaker and the coat
= 3 u
= 3 x 15
= $45

Cost of the windbreaker
= 45 - 7.70
= $37.30

Total cost of the sweater and the blouse
= 5 u
= 5 x 15
= $75

Cost of the blouse
= 75 - 17.30
= $57.70

Difference in cost between the blouse and the windbreaker
= 57.70 - 37.30
= $20.40

Answer(s): $20.40