a: \(\left\{{}\begin{matrix}2x+3y=1\\x-y=3\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x+3y=1\\2x-2y=6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}5y=-5\\x-y=3\end{matrix}\right.\Leftrightarrow y=-1;x=3+y=3-1=2\)
b: \(\Leftrightarrow\left\{{}\begin{matrix}12x-8y=44\\12x-15y=9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}7y=35\\4x-5y=3\end{matrix}\right.\)
=>y=5; 4x=3+5y=3+25=28
=>x=7; y=5
c: \(\Leftrightarrow\left\{{}\begin{matrix}5x=10\\2x-y=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=-3\end{matrix}\right.\)
d: \(\Leftrightarrow\left\{{}\begin{matrix}4x=4\\2x-y=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=2\end{matrix}\right.\)
