Решение:

а) $$rac{3}{8} \cdot \frac{9}{11} = \frac{3 \cdot 9}{8 \cdot 11} = \frac{27}{88}$$

б) $$rac{22}{35} \cdot \frac{21}{44} = \frac{22 \cdot 21}{35 \cdot 44} = \frac{11 \cdot 2 \cdot 7 \cdot 3}{7 \cdot 5 \cdot 11 \cdot 4} = \frac{2 \cdot 3}{5 \cdot 4} = \frac{6}{20} = \frac{3}{10}$$

в) $$5\frac{3}{5} \cdot 1\frac{4}{21} = \frac{28}{5} \cdot \frac{25}{21} = \frac{28 \cdot 25}{5 \cdot 21} = \frac{4 \cdot 7 \cdot 5 \cdot 5}{5 \cdot 7 \cdot 3} = \frac{4 \cdot 5}{3} = \frac{20}{3} = 6\frac{2}{3}$$

г) $$9\frac{3}{7} \cdot 1\frac{3}{11} = \frac{66}{7} \cdot \frac{14}{11} = \frac{66 \cdot 14}{7 \cdot 11} = \frac{6 \cdot 11 \cdot 2 \cdot 7}{7 \cdot 11} = 6 \cdot 2 = 12$$

д) $$1\frac{1}{15} \cdot \frac{5}{16} = \frac{16}{15} \cdot \frac{5}{16} = \frac{16 \cdot 5}{15 \cdot 16} = \frac{5}{15} = \frac{1}{3}$$

e) $$rac{7}{11} \cdot 2\frac{5}{14} = \frac{7}{11} \cdot \frac{33}{14} = \frac{7 \cdot 33}{11 \cdot 14} = \frac{7 \cdot 3 \cdot 11}{11 \cdot 2 \cdot 7} = \frac{3}{2} = 1\frac{1}{2}$$