Đáp án:
$\begin{array}{l}
1)\frac{2}{x} < 1\\
\Rightarrow \frac{2}{x} - 1 < 0\\
\Rightarrow \frac{{2 - x}}{x} < 0\\
\Rightarrow \left[ \begin{array}{l}
\left\{ \begin{array}{l}
2 - x < 0\\
x > 0
\end{array} \right.\\
\left\{ \begin{array}{l}
2 - x > 0\\
x < 0
\end{array} \right.
\end{array} \right.\\
\Rightarrow \left[ \begin{array}{l}
x > 2\\
x < 0
\end{array} \right.\\
\Rightarrow B\\
2)\left| {{x^2} - 7x + 12} \right| = - {x^2} + 7x - 12\\
\Rightarrow {x^2} - 7x + 12 \le 0\\
\Rightarrow \left( {x - 3} \right)\left( {x - 4} \right) \le 0\\
\Rightarrow 3 \le x \le 4\\
\Rightarrow C
\end{array}$