Решение:
- \( \frac{1}{6} : \frac{2}{5} = \frac{1}{6} \times \frac{5}{2} = \frac{5}{12} \).
- \( \frac{2}{3} : \frac{1}{2} = \frac{2}{3} \times \frac{2}{1} = \frac{4}{3} \).
- \( \frac{3}{5} : \frac{1}{4} = \frac{3}{5} \times \frac{4}{1} = \frac{12}{5} \).
- \( \frac{1}{2} : \frac{5}{8} = \frac{1}{2} \times \frac{8}{5} = \frac{8}{10} = \frac{4}{5} \).
- \( \frac{5}{12} : \frac{1}{5} = \frac{5}{12} \times \frac{5}{1} = \frac{25}{12} \).
- \( \frac{3}{8} : \frac{1}{4} = \frac{3}{8} \times \frac{4}{1} = \frac{12}{8} = \frac{3}{2} \).
Ответ: 1) 5:12; 2) 4:3; 3) 12:5; 4) 4:5; 5) 25:12; 6) 3:2.