1) $$ \frac{5}{8} \cdot \frac{4}{15} = \frac{5 \cdot 4}{8 \cdot 15} = \frac{20}{120} = \frac{1}{6} $$
2) $$ 6\frac{3}{4} \cdot 1\frac{11}{45} = \frac{6 \cdot 4 + 3}{4} \cdot \frac{1 \cdot 45 + 11}{45} = \frac{27}{4} \cdot \frac{56}{45} = \frac{27 \cdot 56}{4 \cdot 45} = \frac{1512}{180} = \frac{42}{5} = 8\frac{2}{5} $$
3) $$ \frac{11}{18} \cdot 36 = \frac{11 \cdot 36}{18} = \frac{396}{18} = 22 $$
Ответ: 1) $$\frac{1}{6}$$; 2) $$8\frac{2}{5}$$; 3) $$22$$