Sarah buys a jacket, a shirt, a sweater and a windbreaker. The average cost of these items is $34. The total cost of the sweater and the windbreaker is ³₅ of the total cost of the jacket and the shirt. If the jacket costs $19.90 and the windbreaker costs $8.70, find the difference in cost between the shirt and the sweater.
Total cost of the 4 items
= 4 x 34
= $136

Total cost of the sweater and the windbreaker = 3 u
Total cost of the jacket and the shirt = 5 u

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

8 u = 136

1 u = 136 ÷ 8 = 17

Total cost of the sweater and the windbreaker
= 3 u
= 3 x 17
= $51

Cost of the sweater
= 51 - 8.70
= $42.30

Total cost of the jacket and the shirt
= 5 u
= 5 x 17
= $85

Cost of the shirt
= 85 - 19.90
= $65.10

Difference in cost between the shirt and the sweater
= 65.10 - 42.30
= $22.80

Answer(s): $22.80