\[ 5m - 3n + 2m - 7n = (5m + 2m) + (-3n - 7n) = 7m - 10n \]
\[ 3(2b - 2) - 2(3b + 1) = (6b - 6) - (6b + 2) = 6b - 6 - 6b - 2 = (6b - 6b) + (-6 - 2) = 0 - 8 = -8 \]
Ответ: а) 7m - 10n; б) -8.