\(\left\{{}\begin{matrix}12x-4y=-16\\3x-y=-4\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}12x-4y=-16\\y=3x+4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}12x-4\left(3x+4\right)=-16\\y=3x+4\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}0x=0\\y=3x+4\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x\in R\\y=3x+4\end{matrix}\right.\)