\[\left\{ \begin{matrix} y - x = - 3 \\ 2x + y = 9\ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} y = x - 3\ \ \ \ \ \ \ \ \ \ \\ 2x + x - 3 = 9 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} y = x - 3 \\ 3x = 12\ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} x = 4\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ y = 4 - 3 = 1 \\ \end{matrix} \right.\ \]
\[Проверка:\ \]
\[\left\{ \begin{matrix} 1 - 4 = - 3\ \ \\ 2 \cdot 4 + 1 = 9 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} - 3 = - 3 \\ 9 = 9 \\ \end{matrix} \right.\ \Longrightarrow верно.\]
\[Ответ:(4;1).\]