Write the equation out: (total cost: 0.35C[per carton] + 75[delivery charge]) ≤ 500. Subtract 75 on both sides and it would be: 0.35C ≤ 425. Divide 0.35 on both sides and you'll get C ≤ 1214. Therefore, the maximum # of cartons that Elvira can buy is 1214 cartons of milk.
