a) $$18x^2 - (10x - 5 + 18x^2) = 18x^2 - 10x + 5 - 18x^2 = (18x^2 - 18x^2) - 10x + 5 = -10x + 5$$
б) $$-12c^2 + 5c + (c + 11c^2) = -12c^2 + 5c + c + 11c^2 = (-12c^2 + 11c^2) + (5c + c) = -1c^2 + 6c = -c^2 + 6c$$
в) $$(b^2 + b - 1) - (b^2 - b + 1) = b^2 + b - 1 - b^2 + b - 1 = (b^2 - b^2) + (b + b) + (-1 - 1) = 2b - 2$$
г) $$(15 - 7y^2) - (y^3 - y^2 - 15) = 15 - 7y^2 - y^3 + y^2 + 15 = -y^3 + (-7y^2 + y^2) + (15 + 15) = -y^3 - 6y^2 + 30$$
Ответ: a) $$-10x + 5$$; б) $$-c^2 + 6c$$; в) $$2b - 2$$; г) $$-y^3 - 6y^2 + 30$$