Gillian buys a blouse, a skirt, a vest and a blazer. The average cost of these items is $28. The total cost of the vest and the blazer is ²₅ of the total cost of the blouse and the skirt. If the blouse costs $17.60 and the blazer costs $8.30, find the difference in cost between the skirt and the vest.
Total cost of the 4 items
= 4 x 28
= $112

Total cost of the vest and the blazer = 2 u
Total cost of the blouse and the skirt = 5 u

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

7 u = 112

1 u = 112 ÷ 7 = 16

Total cost of the vest and the blazer
= 2 u
= 2 x 16
= $32

Cost of the vest
= 32 - 8.30
= $23.70

Total cost of the blouse and the skirt
= 5 u
= 5 x 16
= $80

Cost of the skirt
= 80 - 17.60
= $62.40

Difference in cost between the skirt and the vest
= 62.40 - 23.70
= $38.70

Answer(s): $38.70