1) 2/3 · 1/4 2) 7/12 : 3/10 3) 1/2 : 3/4 4) 5/14 : 10/21

Решение:

1. \( \frac{2}{3} \cdot \frac{1}{4} = \frac{2}{12} = \frac{1}{6} \)
2. \( \frac{7}{12} : \frac{3}{10} = \frac{7}{12} \cdot \frac{10}{3} = \frac{70}{36} = \frac{35}{18} \)
3. \( \frac{1}{2} : \frac{3}{4} = \frac{1}{2} \cdot \frac{4}{3} = \frac{4}{6} = \frac{2}{3} \)
4. \( \frac{5}{14} : \frac{10}{21} = \frac{5}{14} \cdot \frac{21}{10} = \frac{105}{140} = \frac{21}{28} = \frac{3}{4} \)

Ответ: 1) \( \frac{1}{6} \); 2) \( \frac{35}{18} \); 3) \( \frac{2}{3} \); 4) \( \frac{3}{4} \).