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 3 large boxes and 5 small boxes has a total weight of 121 kilograms. A delivery of 6 large boxes and 2 small boxes has a total weight of 131 kilograms. How much does each type of box weigh?

Answer 1

3L +5S = 121

6L+ 2S = 131

multiply 1st equation by 2 and subtract the 2nd equation

6L+10S =242

6L + 2S =131

8S = 111

S = 111/8 = 13 7/8 kg

= 13.875 kg

L = (121-5(111/8))/3 = (121- 555/8)/3 = 413/8/3

= 413/24

= 17 5/24 kg

= 17.208333...kg

3L=51 5/8

5S = 69 3/8

3L+5S = 111

6L = 103 1/4

2S = 27 3/4

6L+2S = 131