Выполнение действий с дробями

1. а) $$rac{b-3}{2b}+rac{b+12}{8b} = rac{4(b-3)+b+12}{8b} = rac{4b-12+b+12}{8b} = rac{5b}{8b} = rac{5}{8}$$
2. б) $$rac{1}{n-5}-rac{1}{n+5} = rac{(n+5)-(n-5)}{(n-5)(n+5)} = rac{n+5-n+5}{n^2-25} = rac{10}{n^2-25}$$