Subtract 15mn – 22m +2n from 14mn – 12m +7n.

Subtract the entire expression by changing the signs of its terms: (14mn – 12m + 7n) – (15mn – 22m + 2n) = 14mn – 12m + 7n – 15mn + 22m – 2n. Combine like terms to get –mn + 10m + 5n, which is choice A.

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