Shiyun buys a blazer, a skirt, a jumpsuit and a jacket. The average cost of these items is $35. The total cost of the jumpsuit and the jacket is ³₄ of the total cost of the blazer and the skirt. If the blazer costs $10.60 and the jacket costs $6.40, find the difference in cost between the skirt and the jumpsuit.
Total cost of the 4 items
= 4 x 35
= $140

Total cost of the jumpsuit and the jacket = 3 u
Total cost of the blazer and the skirt = 4 u

Total cost of the 4 items
= 3 u + 4 u
= 7 u

7 u = 140

1 u = 140 ÷ 7 = 20

Total cost of the jumpsuit and the jacket
= 3 u
= 3 x 20
= $60

Cost of the jumpsuit
= 60 - 6.40
= $53.60

Total cost of the blazer and the skirt
= 4 u
= 4 x 20
= $80

Cost of the skirt
= 80 - 10.60
= $69.40

Difference in cost between the skirt and the jumpsuit
= 69.40 - 53.60
= $15.80

Answer(s): $15.80