а) \( \frac{4}{5} : \frac{9}{11} = \frac{4}{5} \cdot \frac{11}{9} = \frac{44}{45} \)
б) \( \frac{1}{5} : \frac{5}{7} = \frac{1}{5} \cdot \frac{7}{5} = \frac{7}{25} \)
в) \( \frac{2}{9} : \frac{2}{9} = 1 \)
г) \( \frac{7}{8} : \frac{1}{13} = \frac{7}{8} \cdot \frac{13}{1} = \frac{91}{8} \)
д) \( \frac{5}{1} : \frac{1}{2} = 5 \cdot 2 = 10 \)
е) \( \frac{5}{2} : \frac{5}{7} = \frac{5}{2} \cdot \frac{7}{5} = \frac{7}{2} \)
ж) \( \frac{12}{25} : \frac{8}{15} = \frac{12}{25} \cdot \frac{15}{8} = \frac{12 \cdot 15}{25 \cdot 8} = \frac{(3 \cdot 4) \cdot (3 \cdot 5)}{(5 \cdot 5) \cdot (2 \cdot 4)} = \frac{3 \cdot 3}{5 \cdot 2} = \frac{9}{10} \)
Ответ: а) \(\frac{44}{45}\); б) \(\frac{7}{25}\); в) 1; г) \(\frac{91}{8}\); д) 10; е) \(\frac{7}{2}\); ж) \(\frac{9}{10}\).