Jane buys a jacket, a dress, a shirt and a blouse. The average cost of these items is $45. The total cost of the shirt and the blouse is ⁴₅ of the total cost of the jacket and the dress. If the jacket costs $15.40 and the blouse costs $8.80, find the difference in cost between the dress and the shirt.
Total cost of the 4 items
= 4 x 45
= $180

Total cost of the shirt and the blouse = 4 u
Total cost of the jacket and the dress = 5 u

Total cost of the 4 items
= 4 u + 5 u
= 9 u

9 u = 180

1 u = 180 ÷ 9 = 20

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

Cost of the shirt
= 80 - 8.80
= $71.20

Total cost of the jacket and the dress
= 5 u
= 5 x 20
= $100

Cost of the dress
= 100 - 15.40
= $84.60

Difference in cost between the dress and the shirt
= 84.60 - 71.20
= $13.40

Answer(s): $13.40