How much does each type of box weigh

Question

A fruit company delivers its fruit in two types of boxes: large and small. A delivery of 5

 large boxes and 2

 small boxes has a total weight of 78

 kilograms. A delivery of 3

 large boxes and 8

 small boxes has a total weight of 91

 kilograms. How much does each type of box weigh?

Answer 1

5L + 2S = 78

3L + 8S = 91

20L + 8S = 312

3L +8S = 91

17L = 221

L = 221/17 = 13 kilos

2S = 78-5(13) = 78-65 = 13

S = 13/2 = 6.5 kilos