Joelle buys a skirt, a dress, a sweater and a blazer. The average cost of these items is $33. The total cost of the sweater and the blazer is ⁵₆ of the total cost of the skirt and the dress. If the skirt costs $11.70 and the blazer costs $15.50, find the difference in cost between the dress and the sweater.
Total cost of the 4 items
= 4 x 33
= $132

Total cost of the sweater and the blazer = 5 u
Total cost of the skirt and the dress = 6 u

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

11 u = 132

1 u = 132 ÷ 11 = 12

Total cost of the sweater and the blazer
= 5 u
= 5 x 12
= $60

Cost of the sweater
= 60 - 15.50
= $44.50

Total cost of the skirt and the dress
= 6 u
= 6 x 12
= $72

Cost of the dress
= 72 - 11.70
= $60.30

Difference in cost between the dress and the sweater
= 60.30 - 44.50
= $15.80

Answer(s): $15.80