Answer :
[tex]3x+8y=-1 \\
\underline{-3x+y=-17} \\
8y+y=-1-17 \\
9y=-18 \\
y=\frac{-18}{9} \\
y=-2 \\ \\
-3x+y=-17 \\
-3x-2=-17 \\
-3x=-17+2 \\
-3x=-15 \\
x=\frac{-15}{-3} \\
x=5 \\ \\
\boxed{(x,y)=(5,-2)}[/tex]
[tex] \left \{ {{3x+8y=-1} \atop {-3x+y=-14}} \right. \\+-------\\add\ both\ equations\\\\
9y=-15 \ \ \ | divide\ by\ 9\\\\
y=-\frac{15}{9}=-\frac{5}{3}\\\\
3x=-1-8y\ \ \| divide\ by\ 3\\\\
x=\frac{-1-8y}{3}=\frac{-1-8*(-\frac{5}{3})}{3}=\frac{-1+\frac{40}{3}}{3}=\frac{37}{3}*\frac{1}{3}=\frac{37}{3}[/tex]
