Simon buys a blazer, a windbreaker and a vest. The average cost of these items is $84. The cost of the vest is four times the total cost of the blazer and the windbreaker. If the blazer costs $20, find the difference in cost between the windbreaker and the vest.
Total cost of the 3 items
= 3 x 84
= $252

Total cost of the blazer and the windbreaker = 1 u
Cost of the vest = 4 u

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

5 u = 252 

1 u = 252 ÷ 5 = 50.40

Total cost of the blazer and the windbreaker = $50.40

Cost of the windbreaker 
= 50.40 - 20
= $30.40

Cost of the vest
= 4 u
= 4 x 50.40
= $201.60

Difference in cost between the windbreaker and the vest
= 201.60 - 30.40
= $171.20

Answer(s): $171.20