Выполнение действий с дробями

1. a) $$\frac{y-6}{3y} + \frac{y+15}{4y} = \frac{4(y-6) + 3(y+15)}{12y} = \frac{4y-24+3y+45}{12y} = \frac{7y+21}{12y} = \frac{7(y+3)}{12y}$$
2. b) $$\frac{1}{m-6} - \frac{1}{m+6} = \frac{(m+6) - (m-6)}{(m-6)(m+6)} = \frac{m+6-m+6}{m^2 - 36} = \frac{12}{m^2 - 36}$$