Answer:
Step-by-step explanation:
If x and y represent the number of math and science books you're carrying, respectively, then 3x and 4y represent their weights in pounds.
The total weight of the carry will be 3x+4y, and you want that to be at most 24 pounds. The expression modeling this is ...
... 3x +4y ≤ 24
A graph of this inequality is shown in the attachment. (We have added the constraints that the number of books not be negative.)
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5 math books will weigh 5·3 = 15 pounds, so will be within the limit you can carry.