a) \( \frac{9}{10} - \frac{2}{5} = \frac{9}{10} - \frac{4}{10} = \frac{5}{10} \)
б) \( \frac{3}{5} - \frac{4}{15} = \frac{9}{15} - \frac{4}{15} = \frac{5}{15} \)
в) \( \frac{7}{12} - \frac{8}{15} = \frac{35}{60} - \frac{32}{60} = \frac{3}{60} \)
г) \( \frac{25}{39} - \frac{15}{26} = \frac{50}{78} - \frac{45}{78} = \frac{5}{78} \)
a) \( \frac{5}{10} \)
б) \( \frac{5}{15} \)
в) \( \frac{3}{60} \)
г) \( \frac{5}{78} \)