Answer :
[tex] \left \{ {{-x+y=-5} \ \ |(-4) \atop {-3x+4y=-12}} \right. \\\\ \left \{ {{4x-4y=20} \atop {-3x+4y=-12}} \right. \\ ======== \\ \boxed{x \ / =8} \\\\ -x+y=-5 \\\\ -8+y=-5 \\\\ y=-5+8 \\\\ \boxed{y=3}[/tex]
[tex]-x+y=-5|\cdot(-3)\\
-3x+4y=-12\\\\
3x-3y=15\\
\underline{-3x+4y=-12}\\
y=3\\\\
-x+3=-5\\
-x=-8\\
x=8\\\\
\boxed{x=8,y=3}
[/tex]
