Выполни действия

\(\dfrac{a}{m}+\dfrac{b}{m}=\dfrac{a+b}{m}\) , \(\dfrac{a}{n}-\dfrac{b}{n}=\dfrac{a-b}{n}\!\) .

1. \(\dfrac{5a-b}{3c}+ \dfrac{a-2b}{3c}\) \(\mathrlap{\;=}\) [ ] \(\mathrlap{\;=}\) [ ] \(\mathrlap{\;=}\) \({=\dfrac{2a-b}{c}}\) .

2. \(\dfrac{2n-3}{5n^2} - \dfrac{7n-3}{5n^2}=\) [ ].