a) \frac{5}{9}:5 = \frac{5}{9} \cdot \frac{1}{5} = \frac{1}{9};
б) \frac{4}{7}:4 = \frac{4}{7} \cdot \frac{1}{4} = \frac{1}{7};
в) 1:\frac{5}{13} = 1 \cdot \frac{13}{5} = \frac{13}{5} = 2\frac{3}{5};
г) 7:\frac{4}{7} = 7 \cdot \frac{7}{4} = \frac{49}{4} = 12\frac{1}{4};
д) 4:\frac{8}{9} = 4 \cdot \frac{9}{8} = \frac{9}{2} = 4\frac{1}{2}.
Ответ: а) \frac{1}{9}; б) \frac{1}{7}; в) 2\frac{3}{5}; г) 12\frac{1}{4}; д) 4\frac{1}{2}.