we need to solve Y on each equation
1)
[tex]\begin{gathered} x-3y=12 \\ \\ -3y=12-x \\ y=\frac{12-x}{-3} \\ \\ y=\frac{1}{3}x-4 \end{gathered}[/tex]2)
[tex]\begin{gathered} x+5y=-15 \\ 5y=-15-x \\ y=\frac{-x-15}{5} \\ \\ y=-\frac{1}{5}x-3 \end{gathered}[/tex]