\[\left\{ \begin{matrix} 2x = 9\ \ \ \ \ \ \ \ \\ 4x - y = 8 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} x = 4,5\ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ 4 \cdot 4,5 - y = 8 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} x = 4,5\ \ \ \ \ \ \ \\ 18 - y = 8 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} x = 4,5 \\ y = 10\ \ \\ \end{matrix} \right.\ \]
\[Ответ:(4,5;10).\]