Henry had a sum of money. If he bought 7 tarts and 5 wafers, he would be short of $16. If he bought 2 tarts and 3 wafers, he would have $11 left. Given that he had $35, how many wafers could he buy at most?
Cost of 1 tart = 1 T
Cost of 1 wafer = 1 W

7 T + 5 W - 16 = 35
7 T + 5 W = 35 + 16 
7 T + 5 W = 51 --- (1)

2 T + 3 W + 11 = 35 
2 T + 3 W = 35 - 11 
2 T + 3 W = 24 --- (2)

Make T the same.

(1) _{x 2}
14 T + 10 W = 102 
14 T = 102 - 10 W ---- (3)

(2) _{x 7}
14 T + 21 W = 168 
14 T = 168 - 21 W ---- (4)

(3) = (4)
102 - 10 W = 168 - 21 W 
21 W - 10 W = 168 - 102 
11 W = 66

1 W = 66 ÷ 11 = 6 

Cost of 1 wafer = $6 

Number of wafers that Henry can buy at most
= 35 ÷ 6
= 5 r 5

Most number of wafers that Henry can buy = 5

Answer(s): 5