a) 9 10 - 1 15; б) 5 16 + 5 12; в) 2 15 + 3 20; г) 14 15 - 7 25.

а)
\( \frac{9}{10} - \frac{1}{15} = \frac{27}{30} - \frac{2}{30} = \frac{25}{30} = \frac{5}{6} \)

б)
\( \frac{5}{16} + \frac{5}{12} = \frac{15}{48} + \frac{20}{48} = \frac{35}{48} \)

в)
\( \frac{2}{15} + \frac{3}{20} = \frac{8}{60} + \frac{9}{60} = \frac{17}{60} \)

г)
\( \frac{14}{15} - \frac{7}{25} = \frac{70}{75} - \frac{21}{75} = \frac{49}{75} \)