The total cost of 9 jumpsuits and 9 skirts was $513. Tina bought 11 such jumpsuits, 9 such skirts and a cardigan for $618. If the total cost of a windbreaker and a jumpsuit was $67, find the difference in cost between the jumpsuit and the windbreaker.
Let 1 J be 1 jumpsuit.
Let 1 S be 1 skirt.
Let 1 W be 1 windbreaker.

9 J + 9 S = 513 --- (1)

1 J + 1 S = 513 ÷ 9
1 J + 1 S = 57 --- (2)

1 J + 1 W = 67 --- (3)

11 J + 9 S + 1 W = 618 --- (4)

(4) - (1)
(11 J + 9 S + 1 W) - (9 J + 9 S) = 618 - 513 
11 J - 9 J + 9 S - 9 S + 1 W = 105

2 J + 1 W = 105 --- (5)

(5) - (3)
(2 J + 1 W) - (1 J + 1 W) = 105 - 67
2 J - 1 J + 1 W - 1 W = 38
2 J - 1 J = 38

1 J = 38

From (3)
1 J + 1 W = 67
38 + 1 W = 67

1 W = 67 - 38 = 29

Difference in the cost between the jumpsuit and the windbreaker
= 1 J - 1 W
= 38 - 29
= $9

Answer(s): $9