Flynn buys a blouse, a vest and a windbreaker. The average cost of these items is $77. The cost of the windbreaker is four times the total cost of the blouse and the vest. If the blouse costs $21, find the difference in cost between the vest and the windbreaker.
Total cost of the 3 items
= 3 x 77
= $231

Total cost of the blouse and the vest = 1 u
Cost of the windbreaker = 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 blouse and the vest = $46.20

Cost of the vest 
= 46.20 - 21
= $25.20

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

Difference in cost between the vest and the windbreaker
= 184.80 - 25.20
= $159.60

Answer(s): $159.60