The total cost of 9 jackets and 9 blazers was $495. Tina bought 11 such jackets, 9 such blazers and a cardigan for $596. If the total cost of a skirt and a jacket was $61, find the difference in cost between the jacket and the skirt.
Let 1 J be 1 jacket.
Let 1 B be 1 blazer.
Let 1 S be 1 skirt.

9 J + 9 B = 495 --- (1)

1 J + 1 B = 495 ÷ 9
1 J + 1 B = 55 --- (2)

1 J + 1 S = 61 --- (3)

11 J + 9 B + 1 S = 596 --- (4)

(4) - (1)
(11 J + 9 B + 1 S) - (9 J + 9 B) = 596 - 495 
11 J - 9 J + 9 B - 9 B + 1 S = 101

2 J + 1 S = 101 --- (5)

(5) - (3)
(2 J + 1 S) - (1 J + 1 S) = 101 - 61
2 J - 1 J + 1 S - 1 S = 40
2 J - 1 J = 40

1 J = 40

From (3)
1 J + 1 S = 61
40 + 1 S = 61

1 S = 61 - 40 = 21

Difference in the cost between the jacket and the skirt
= 1 J - 1 S
= 40 - 21
= $19

Answer(s): $19