9. a) 5/6 - 3/8 9. б) 9/14 - 9/21 9. в) 7/20 - 7/30

Решение:

• a) \( \frac{5}{6} - \frac{3}{8} = \frac{20}{24} - \frac{9}{24} = \frac{11}{24} \)
• б) \( \frac{9}{14} - \frac{9}{21} = \frac{27}{42} - \frac{18}{42} = \frac{9}{42} = \frac{3}{14} \)
• в) \( \frac{7}{20} - \frac{7}{30} = \frac{21}{60} - \frac{14}{60} = \frac{7}{60} \)

Ответ: а) 11/24, б) 3/14, в) 7/60