Решение:
- \( \frac{5}{6} \cdot \frac{3}{20} = \frac{5 \cdot 3}{6 \cdot 20} = \frac{15}{120} = \frac{1}{8} \)
- \( \frac{3}{7} \cdot \frac{6}{11} = \frac{3 \cdot 6}{7 \cdot 11} = \frac{18}{77} \)
- \( \frac{10}{11} \cdot \frac{11}{26} = \frac{10 \cdot 11}{11 \cdot 26} = \frac{10}{26} = \frac{5}{13} \)
Ответ: 1) \( \frac{1}{8} \); 2) \( \frac{18}{77} \); 3) \( \frac{5}{13} \).