Question

Answer 1

\(c,\left\{{}\begin{matrix}10x-9y=1\\15x+21y=36\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}10x-9y=1\\5x+7y=12\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}10x-9y=1\\10x+14y=24\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}10x-9y=1\\-23y=-23\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}10x-9.1=1\\y=1\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\y=1\end{matrix}\right.\)