The total cost of 6 sweaters and 6 blazers was $288. Tina bought 8 such sweaters, 6 such blazers and a cardigan for $394. If the total cost of a vest and a sweater was $70, find the difference in cost between the sweater and the vest.
Let 1 S be 1 sweater.
Let 1 B be 1 blazer.
Let 1 V be 1 vest.

6 S + 6 B = 288 --- (1)

1 S + 1 B = 288 ÷ 6
1 S + 1 B = 48 --- (2)

1 S + 1 V = 70 --- (3)

8 S + 6 B + 1 V = 394 --- (4)

(4) - (1)
(8 S + 6 B + 1 V) - (6 S + 6 B) = 394 - 288 
8 S - 6 S + 6 B - 6 B + 1 V = 106

2 S + 1 V = 106 --- (5)

(5) - (3)
(2 S + 1 V) - (1 S + 1 V) = 106 - 70
2 S - 1 S + 1 V - 1 V = 36
2 S - 1 S = 36

1 S = 36

From (3)
1 S + 1 V = 70
36 + 1 V = 70

1 V = 70 - 36 = 34

Difference in the cost between the sweater and the vest
= 1 S - 1 V
= 36 - 34
= $2

Answer(s): $2