1. а) 3ac * 5ab = 15a^2bc
б) 10x * 9y *(-7a) = -630axy
4. 8m + 2 - (5 + 7m) - 4m = 8m + 2 - 5 - 7m - 4m = -3m - 3 = -3 * 17 - 3 = -54
5. 7(y+2x) - 2(x-2y) = 7y + 14x - 2x + 4y = 12x + 11y
7. 2c - (3c + (2c - (c+1)) + 3) = 2c - (3c + 2c - c - 1 +3) = 2c - 3c - 2c + c + 1 - 3 = -2c - 2 = 2(-c-1)