Find the sum of the given polynomials.
5m + 2n, n - 3m, and 7 - 3n
7 - 2m
2m + 7
14m + 5n - 6
9m
5m + 2n, n - 3m, and 7 - 3n
7 - 2m
2m + 7
14m + 5n - 6
9m