Gillian buys a blouse, a sweater, a coat and a blazer. The average cost of these items is $55. The total cost of the coat and the blazer is ⁵₆ of the total cost of the blouse and the sweater. If the blouse costs $13.10 and the blazer costs $6.70, find the difference in cost between the sweater and the coat.
Total cost of the 4 items
= 4 x 55
= $220

Total cost of the coat and the blazer = 5 u
Total cost of the blouse and the sweater = 6 u

Total cost of the 4 items
= 5 u + 6 u
= 11 u

11 u = 220

1 u = 220 ÷ 11 = 20

Total cost of the coat and the blazer
= 5 u
= 5 x 20
= $100

Cost of the coat
= 100 - 6.70
= $93.30

Total cost of the blouse and the sweater
= 6 u
= 6 x 20
= $120

Cost of the sweater
= 120 - 13.10
= $106.90

Difference in cost between the sweater and the coat
= 106.90 - 93.30
= $13.60

Answer(s): $13.60