\[\left\{ \begin{matrix}
x^{2} - 6x + 8 \leq 0 \\
3x - 8 \geq 0\ \ \ \ \ \ \ \ \ \ \\
\end{matrix} \right.\ \]
\[x^{2} - 6x + 8 \leq 0\]
\[D_{1} = 9 - 8 = 1\]
\[x_{1} = 3 + 1 = 4;\ \ x_{2} = 3 - 1 = 2.\]
\[(x - 2)(x - 4) \leq 0\]

\[2 \leq x \leq 4.\]
\[\left\{ \begin{matrix}
2 \leq x \leq 4 \\
3x \geq 8\ \ \ \ \ \ \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\left\{ \begin{matrix}
2 \leq x \leq 4\ \ \ \ \\
x \geq \frac{8}{3} \geq 2\frac{2}{3} \\
\end{matrix} \right.\ \]
\[2\frac{2}{3} \leq x \leq 4.\]
\[Ответ:2\frac{2}{3} \leq x \leq 4.\]