2) а) $$\frac{12a^3b^2}{18a^4} = \frac{2b^2}{3a}$$
б) $$\frac{12a^3b^2 + 6a^2}{18a^4} = \frac{6a^2(2ab^2 + 1)}{18a^4} = \frac{2ab^2 + 1}{3a^2}$$
в) $$\frac{12a^3b^2 + 6a^2}{18a^4 - 3a^2} = \frac{6a^2(2ab^2 + 1)}{3a^2(6a^2 - 1)} = \frac{2(2ab^2 + 1)}{6a^2 - 1}$$
г) $$\frac{a^2 + ab}{a} = \frac{a(a+b)}{a} = a + b$$