a) $$\frac{3}{5} \cdot \frac{4}{3} = \frac{3 \cdot 4}{5 \cdot 3} = \frac{12}{15} = \frac{4}{5}$$
б) $$\frac{2}{5} \cdot \frac{9}{8} = \frac{2 \cdot 9}{5 \cdot 8} = \frac{18}{40} = \frac{9}{20}$$
в) $$\frac{4}{11} \cdot 11 = \frac{4 \cdot 11}{11} = 4$$
г) $$\frac{1}{8} \cdot \frac{16}{5} = \frac{1 \cdot 16}{8 \cdot 5} = \frac{16}{40} = \frac{2}{5}$$
д) $$\frac{11}{20} \cdot 5 = \frac{11 \cdot 5}{20} = \frac{55}{20} = \frac{11}{4} = 2 \frac{3}{4}$$
Ответ: а) 4/5, б) 9/20, в) 4, г) 2/5, д) 11/4