4 7 - · - = 7 8 12: 6 = 13 3 8 - · - = 4 9 7 1 -: - = 12 3 3 3 -: - = 8 4

Решение:

1. $$\frac{4}{7} \cdot \frac{7}{8} = \frac{4 \cdot 7}{7 \cdot 8} = \frac{28}{56} = \frac{1}{2}$$
2. $$\frac{12}{13} : 6 = \frac{12}{13} : \frac{6}{1} = \frac{12}{13} \cdot \frac{1}{6} = \frac{12 \cdot 1}{13 \cdot 6} = \frac{12}{78} = \frac{2}{13}$$
3. $$\frac{3}{4} \cdot \frac{8}{9} = \frac{3 \cdot 8}{4 \cdot 9} = \frac{24}{36} = \frac{2}{3}$$
4. $$\frac{7}{12} : \frac{1}{3} = \frac{7}{12} \cdot \frac{3}{1} = \frac{7 \cdot 3}{12 \cdot 1} = \frac{21}{12} = \frac{7}{4} = 1\frac{3}{4}$$
5. $$\frac{3}{8} : \frac{3}{4} = \frac{3}{8} \cdot \frac{4}{3} = \frac{3 \cdot 4}{8 \cdot 3} = \frac{12}{24} = \frac{1}{2}$$

Ответ:

1. $$\frac{1}{2}$$
2. $$\frac{2}{13}$$
3. $$\frac{2}{3}$$
4. $$1\frac{3}{4}$$
5. $$\frac{1}{2}$$