The equivalent expression to this problem is 9m + 20. This would be option B.
We can begin by distributing -1 into everything inside the parenthesis:
-1 • 2m = -2m
-1 • -8 = 8
Now we can remove parenthesis:
5m - 2m + 8 + 12 + 6m
Finally, let’s combine like terms to find our expression:
(5m - 2m + 6m) + (8 + 12)
9m + 20
Hence, option B is correct.