Let:
[tex]\begin{gathered} -x+2y=-15_{\text{ }}(1) \\ 8x-2y=-20_{\text{ }}(2) \end{gathered}[/tex]Using elimination:
[tex]\begin{gathered} (1)+(2) \\ -x+8x+2y-2y=-15-20 \\ 7x=-35 \end{gathered}[/tex]Solve for x:
Divide both sides by 7:
[tex]\begin{gathered} \frac{7x}{7}=-\frac{35}{7} \\ x=-5 \end{gathered}[/tex]Replace the value of x into (1):
[tex]\begin{gathered} 5+2y=-15 \\ 2y=-20 \\ y=-\frac{20}{2} \\ y=-10 \end{gathered}[/tex]