1) 5a + 7b - 2a - 8b = 5a - 2a + 7b - 8b = 3a - b;
2) 3(4x + 2) - 5 = 12a + 6 - 5 = 12a + 1;
3) 20b - (b - 3) + (3b - 10) = 20b - b + 3 + 3b - 10 = 22b - 7.
1) 5a + 7b - 2a - 8b = 5a - 2a + 7b - 8b = 3a - b;
2) 3(4x + 2) - 5 = 12a + 6 - 5 = 12a + 1;
3) 20b - (b - 3) + (3b - 10) = 20b - b + 3 + 3b - 10 = 22b - 7.