\(\left\{{}\begin{matrix}2x+3y=8\\-x+y=-4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+3\left(x-4\right)=8\\y=x-4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2x+3x-12=8\\y=x-4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}5x=20\\y=x-4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{20}{5}=4\\y=4-4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=4\\y=0\end{matrix}\right.\)
\(\left\{{}\begin{matrix}2x+3y=8\\-x+y=-4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+3\left(x-4\right)=8\\y=-4+x\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}5x-12=8\\y=-4+x\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=4\\y=0\end{matrix}\right.\)
