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