\[\left\{ \begin{matrix} x - 2y = 9\ \ \\ 3x + 4y = 7 \\ \end{matrix} \right.\ \]
\[\left\{ \begin{matrix} x = 9 + 2y\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ 3(9 + 2y) + 4y = 7 \\ \end{matrix} \right.\ \]
\[27 + 6y + 4y - 7 = 0\]
\[10y = - 20\]
\[y = - 2.\]
\[x = 9 + 2 \cdot ( - 2) = 9 - 4 = 5.\]
\[Ответ:(5;\ - 2).\]