б) $$rac{6}{2m-m^2} - \frac{3}{m} = \frac{6}{m(2-m)} - \frac{3}{m} = \frac{6 - 3(2-m)}{m(2-m)} = \frac{6-6+3m}{m(2-m)} = \frac{3m}{m(2-m)} = \frac{3}{2-m}$$