8. Блок 1: 41/50 − 1/5. Блок 2: 21/5 : 6/7. Блок 3: (17/15 − 1/12) · 20/3.

Блок 1. \(\frac{41}{50}-\frac{1}{5}=\frac{41}{50}-\frac{10}{50}=\frac{31}{50}\).

Блок 2. \(\frac{21}{5}:\frac{6}{7}=\frac{21}{5}\cdot\frac{7}{6}=\frac{147}{30}=\frac{49}{10}\).

Блок 3. \(\left(\frac{17}{15}-\frac{1}{12}\right)\cdot\frac{20}{3}=\left(\frac{68}{60}-\frac{5}{60}\right)\cdot\frac{20}{3}=\frac{21}{20}\cdot\frac{20}{3}=7\).