Выражение: -7a-9b+a+11b,a-(a-8)+(12+a,-3(c-5)+6(c+3)

- 7а - 9b + a + 11b = (a - 7a) + (11b - 9b) = - 6a + 2b = 2b - 6a

a - (a - 8) + (12 + a) = a - a + 8 + 12 + a = (a - a + a) + (8 + 12) = a + 20

- 3(c - 5) + 6(c + 3) = - 3c + 15 + 6c + 18 = (6c - 3c) + (15 + 18) = 3c + 33