Archie buys a coat, a windbreaker and a skirt. The average cost of these items is $77. The cost of the skirt is four times the total cost of the coat and the windbreaker. If the coat costs $20, find the difference in cost between the windbreaker and the skirt.
Total cost of the 3 items
= 3 x 77
= $231

Total cost of the coat and the windbreaker = 1 u
Cost of the skirt = 4 u

Total cost of the 3 items 
= 1 u + 4 u
= 5 u

5 u = 231 

1 u = 231 ÷ 5 = 46.20

Total cost of the coat and the windbreaker = $46.20

Cost of the windbreaker 
= 46.20 - 20
= $26.20

Cost of the skirt
= 4 u
= 4 x 46.20
= $184.80

Difference in cost between the windbreaker and the skirt
= 184.80 - 26.20
= $158.60

Answer(s): $158.60