б) $$2\frac{1}{6}-1\frac{5}{6}+3\frac{2}{6}-2\frac{5}{6}$$

$$\begin{aligned} 2\frac{1}{6}-1\frac{5}{6}+3\frac{2}{6}-2\frac{5}{6} = \frac{13}{6} - \frac{11}{6} + \frac{20}{6} - \frac{17}{6} = \frac{13-11+20-17}{6} = \frac{5}{6} \end{aligned}$$
Ответ: $$\frac{5}{6}$$