Opal buys a jacket, a shirt, a dress and a windbreaker. The average cost of these items is $35. The total cost of the dress and the windbreaker is ³₄ of the total cost of the jacket and the shirt. If the jacket costs $18.10 and the windbreaker costs $17.30, find the difference in cost between the shirt and the dress.
Total cost of the 4 items
= 4 x 35
= $140

Total cost of the dress and the windbreaker = 3 u
Total cost of the jacket and the shirt = 4 u

Total cost of the 4 items
= 3 u + 4 u
= 7 u

7 u = 140

1 u = 140 ÷ 7 = 20

Total cost of the dress and the windbreaker
= 3 u
= 3 x 20
= $60

Cost of the dress
= 60 - 17.30
= $42.70

Total cost of the jacket and the shirt
= 4 u
= 4 x 20
= $80

Cost of the shirt
= 80 - 18.10
= $61.90

Difference in cost between the shirt and the dress
= 61.90 - 42.70
= $19.20

Answer(s): $19.20