\(\frac{m}{5}-\frac{2}{n}=\frac{2}{45}\)
\(\Rightarrow\frac{mn}{5n}-\frac{10}{5n}=\frac{2}{45}\)\(\Rightarrow\frac{mn-10}{5n}=\frac{2}{45}\)
\(\Rightarrow45\left(mn-10\right)=10n\)
\(\Rightarrow45\cdot5\left(mn-2\right)=10n\)
\(\Rightarrow45mn-2=2n\)
\(\Rightarrow45mn-2n=2\)
\(\Rightarrow n\left(45m-2\right)=2\)