Warren had a sum of money. If he bought 7 macarons and 6 croissants, he would be short of $26. If he bought 2 macarons and 3 croissants, he would have $13 left. Given that he had $34, how many croissants could he buy at most?
Cost of 1 macaron = 1 M
Cost of 1 croissant = 1 C

7 M + 6 C - 26 = 34
7 M + 6 C = 34 + 26 
7 M + 6 C = 60 --- (1)

2 M + 3 C + 13 = 34 
2 M + 3 C = 34 - 13 
2 M + 3 C = 21 --- (2)

Make M the same.

(1) _{x 2}
14 M + 12 C = 120 
14 M = 120 - 12 C ---- (3)

(2) _{x 7}
14 M + 21 C = 147 
14 M = 147 - 21 C ---- (4)

(3) = (4)
120 - 12 C = 147 - 21 C 
21 C - 12 C = 147 - 120 
9 C = 27

1 C = 27 ÷ 9 = 3 

Cost of 1 croissant = $3 

Number of croissants that Warren can buy at most
= 34 ÷ 3
= 11 r 1

Most number of croissants that Warren can buy = 11

Answer(s): 11