Đáp án:
$\begin{array}{l}
a)\dfrac{{4x - 1}}{3} - \dfrac{{2 - x}}{{15}} \le \dfrac{{10x - 3}}{5}\\
\Rightarrow \dfrac{{5\left( {4x - 1} \right) - 2 + x}}{{15}} \le \dfrac{{3\left( {10x - 3} \right)}}{{15}}\\
\Rightarrow 20x - 5 - 2 + x \le 30x - 9\\
\Rightarrow 9x \ge 2\\
\Rightarrow x \ge \dfrac{2}{9}\\
b)3x + 3 \le \left| {2x - 7} \right|\\
+ Khi:2x - 7 \ge 0 \Rightarrow x \ge \dfrac{7}{2}\\
\Rightarrow 3x + 3 \le 2x - 7\\
\Rightarrow x \le - 10\left( {ktm} \right)\\
+ Khi:2x - 7 < 0 \Rightarrow x < \dfrac{7}{2}\\
\Rightarrow 3x + 3 \le - 2x + 7\\
\Rightarrow 5x \le 4\\
\Rightarrow x \le \dfrac{4}{5}\\
Vậy\,x \le \dfrac{4}{5}
\end{array}$
(Do giá trị của 2x-7 bằng $\left| {2x - 7} \right|$)
