a) $$\frac{4 \cdot 3}{7 \cdot 8} = \frac{12}{56} = \frac{12:4}{56:4} = \frac{3}{14}$$
Ответ: 3/14
б) $$\frac{2 \cdot 3}{3 \cdot 10} = \frac{6}{30} = \frac{6:6}{30:6} = \frac{1}{5}$$
Ответ: 1/5
в) $$\frac{21 \cdot 6}{21 \cdot 7} = \frac{126}{147} = \frac{126:21}{147:21} = \frac{6}{7}$$
Ответ: 6/7
г) $$\frac{3 \cdot 7}{21 \cdot 24} = \frac{21}{504} = \frac{21:21}{504:21} = \frac{1}{24}$$
Ответ: 1/24