Question

Problem page a delivery truck is transporting boxes of two sizes: large and small. the large boxes weigh 45 pounds each, and the small boxes weigh 15 pounds each. there are 120 boxes in all. if the truck is carrying a total of 3300 pounds in boxes, how many of each type of box is it carrying?

Answer 1

S= number of small boxes
l= number of large boxes

equation 1:  s+l=120
equation 2:  15s+45l=3300

solve by elimination, multiply equation 1 by -15.

-15(s+l=120) =  -15s-15l=-1800  add to equation 2.

-15s+15s-15l+45l=-1800+3300  = 30l=1500

30l=1500 , l=50

s+l=120, s+50=120 --> s=70