x-5y=3
$${\mathtt{y}} = {\frac{\left({\mathtt{3}}{\mathtt{\,-\,}}{\mathtt{x}}\right)}{{\mathtt{5}}}}$$
$${\mathtt{y}} = {\frac{{\mathtt{3}}}{{\mathtt{5}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{x}}}{{\mathtt{5}}}}$$
$${\mathtt{y}} = {\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{5}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{3}}}{{\mathtt{5}}}}$$
Now you can see m= $${\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{5}}}}$$