\[\left\{ \begin{matrix} 4x - 3 \geq x + 6\ \ \ \ \ \\ 5x + 1 \geq 6x - 11 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} 3x \geq 9 \\ x \leq 12 \\ \end{matrix} \right.\ \text{\ \ \ \ \ }\]
\[\left\{ \begin{matrix} x \geq 3\ \ \ \\ x \leq 12 \\ \end{matrix} \right.\ \]
\[Ответ:\lbrack 3;12\rbrack.\]