\(\left\{{}\begin{matrix}3\left(x-y\right)-y=11\\x-2\left(x+5y\right)=-15\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x-3y-y=11\\x-2x-10y=-15\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x-4y=11\\-x-10y=-15\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-10y+15\\3\left(-10y+15\right)-4y=11\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=1\\x=5\end{matrix}\right.\)
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