Tiffany buys a vest, a dress, a sweater and a blouse. The average cost of these items is $28. The total cost of the sweater and the blouse is ³₅ of the total cost of the vest and the dress. If the vest costs $16.70 and the blouse costs $10.30, find the difference in cost between the dress and the sweater.
Total cost of the 4 items
= 4 x 28
= $112

Total cost of the sweater and the blouse = 3 u
Total cost of the vest and the dress = 5 u

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

8 u = 112

1 u = 112 ÷ 8 = 14

Total cost of the sweater and the blouse
= 3 u
= 3 x 14
= $42

Cost of the sweater
= 42 - 10.30
= $31.70

Total cost of the vest and the dress
= 5 u
= 5 x 14
= $70

Cost of the dress
= 70 - 16.70
= $53.30

Difference in cost between the dress and the sweater
= 53.30 - 31.70
= $21.60

Answer(s): $21.60