3. a) 1/9 : 2/3, б) 4/7 : 12/5, в) 9/16 : 3/4, г) 10/21 : 14/15

Решение:

• a) \[ \frac{1}{9} : \frac{2}{3} = \frac{1}{9} \times \frac{3}{2} = \frac{1}{3} \times \frac{1}{2} = \frac{1}{6} \]
• б) \[ \frac{4}{7} : \frac{12}{5} = \frac{4}{7} \times \frac{5}{12} = \frac{1}{7} \times \frac{5}{3} = \frac{5}{21} \]
• в) \[ \frac{9}{16} : \frac{3}{4} = \frac{9}{16} \times \frac{4}{3} = \frac{3}{4} \times \frac{1}{1} = \frac{3}{4} \]
• г) \[ \frac{10}{21} : \frac{14}{15} = \frac{10}{21} \times \frac{15}{14} = \frac{5}{7} \times \frac{5}{7} = \frac{25}{49} \]

Ответ: а) 1/6, б) 5/21, в) 3/4, г) 25/49