System of linear equations

Question

A delivery truck is transporting boxes of two sizes: large and small. The large boxes weigh 45 pounds each, and the small boxes weigh 25 pounds each. There are 130 boxes in all. If the truck is carrying a total of 4650 pounds in boxes, how many of each type of box is it carrying?

Answer 1

L+S = 130

45L + 25S = 4650

multiply first equation by 25

25L + 25S = 130(25) = 3250

subtract it from the 2nd equation to get

20L = 4650 -3250 = 1400 divide by 20

L = 1400/20 = 140/2 = 70 large boxes

S= 130 -70= 60 small boxes

25(70) + 25(60) = 1750 + 1500 = 3250