Hey!
Weight of small box = 5 lb. x no. of small boxes total weight = 5*x
Weight of Large boxes = 12 lb. y no. of large boxes total weight = 12*y
Total weight = 5x + 12y.
Since total weight carrying capacity of shelf is 80, thus the inequality becomes:
5x + 12y Less than or equal to 80.
(a) satisfies the inequality.
(b) satisfies the inequality.
Hope my answer helps!
