\[(1;1;1);\ \ \ x = 1;\ \ y = 1;\ \ z = 1.\]
\[\left\{ \begin{matrix} x - 2y = - 1 \\ 3y + z = 4\ \ \ \\ x - z = 1\ \ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 1 - 2 \cdot 1 = - 1 \\ 3 \cdot 1 + 1 = 4\ \ \ \\ 1 - 1 = 0 \neq 1\ \\ \end{matrix} \right.\ \Longrightarrow нет.\]