\[\boxed{\text{1010\ (1010).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)} - \frac{1}{2} \leq 0,5 - 0,2x \leq \frac{1}{2}\]
\[- 1 \leq - 0,2x \leq 0\]
\[0 \leq 0,2x \leq 1\]
\[0 \leq x \leq 5.\]
\[\textbf{б)} - 100 \leq \frac{20x + 40}{3} \leq 100\]
\[- 300 \leq 20x + 40 \leq 300\]
\[- 340 \leq 20x \leq 260\]
\[- 17 \leq x \leq 13.\]