Algebra way: Prerequisite is to know that if a<b and c<d then (a+c)<(b+d)

Stem: 9n + 3p <= 20 (let's call it inequation A). Is 3n + 3p <= 10 ? (let's call it inequation B)

From the stem, note that n can not be more than 2.23 and p can not be more than 6.67.

This will help when testing values.

(1) - 7n + 5p <= 20 (INSUFFICIENT)

Adding inequation A and (1) gives 16n + 8p <= 40 , divide each side by 8, you get 2n + p <= 5

n=1 p=1 satisfy (1) and inequation A, and statisfy inequation B----- YES

n=0,5 p=3 satisfy (1) and inequation A, but does not statisfy inequation B----- NO

(2) - 4n + 8p <= 20 (SUFFICIENT)

divide each side by 4, you get n + 2p <= 5

Adding "9n + 3p <= 20" and "n + 2p <= 5" gives 10n + 5p <= 25 , divide each side by 5, you get 2n + p <= 5

Adding "2n + p <= 5" and "n + 2p <= 5" gives 3n + 3p <= 10

Answer is B

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