Упростите выражение: 1) $$\frac{2}{3}a \cdot \frac{7}{12}b$$; 2) $$\frac{8}{9}x \cdot 1 \frac{4}{5}y$$; 3) $$5m \cdot 2 \frac{6}{11}n \cdot 2 \frac{5}{14}k$$.

Упростим данные выражения:

1) $$\frac{2}{3}a \cdot \frac{7}{12}b = \frac{2 \cdot 7}{3 \cdot 12}ab = \frac{14}{36}ab = \frac{7}{18}ab$$

2) $$\frac{8}{9}x \cdot 1 \frac{4}{5}y = \frac{8}{9}x \cdot \frac{1 \cdot 5 + 4}{5}y = \frac{8}{9}x \cdot \frac{9}{5}y = \frac{8}{1} \cdot \frac{1}{5}xy = \frac{8}{5}xy = 1 \frac{3}{5}xy$$

3) $$5m \cdot 2 \frac{6}{11}n \cdot 2 \frac{5}{14}k = 5m \cdot \frac{2 \cdot 11 + 6}{11}n \cdot \frac{2 \cdot 14 + 5}{14}k = 5m \cdot \frac{28}{11}n \cdot \frac{33}{14}k = \frac{5}{1} \cdot \frac{28}{11} \cdot \frac{33}{14} \cdot mnk = \frac{5}{1} \cdot \frac{2}{1} \cdot \frac{3}{2}mnk = \frac{30}{1}mnk = 30mnk$$

Ответ: 1) $$\frac{7}{18}ab$$; 2) $$1 \frac{3}{5}xy$$; 3) $$30mnk$$