\[\left\{ \begin{matrix} 3x - 10y = 1\ \ | \cdot 3 \\ 9x + 2y = 67\ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} 9x - 30y = 3 \\ 9x + 2y = 67 \\ \end{matrix} \right.\ ( - )\]
\[- 32y = - 64\]
\[y = 2.\]
\[3x = 1 + 10y = 1 + 10 \cdot 2\]
\[3x = 21\]
\[x = 7.\]
\[\left\{ \begin{matrix} x_{0} = 7 \\ y_{0} = 2 \\ \end{matrix} \right.\ \]
\[x_{0} - y_{0} = 7 - 2 = 5.\]
\[Ответ:3)\ 5.\]