\[\left\{ \begin{matrix} x - y = 0\ \ \ \\ x - 3y = 6 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} x = y\ \ \ \ \ \ \ \ \ \ \\ y - 3y = 6 \\ \end{matrix} \right.\ \text{\ \ \ \ }\]
\[\left\{ \begin{matrix} x = y\ \ \ \ \ \ \\ - 2y = 6 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} y = - 3 \\ x = - 3 \\ \end{matrix} \right.\ \]
\[Проверка:\ \]
\[\left\{ \begin{matrix} - 3 - ( - 3) = 0\ \ \ \ \ \ \\ - 3 - 3 \cdot ( - 3) = 6 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 0 = 0 \\ 6 = 6\ \\ \end{matrix} \right.\ \Longrightarrow верно.\]
\[Ответ:( - 3;\ - 3).\]