Решение:
- \(\left( \frac{1}{2} \cdot \frac{3}{4} - \frac{4}{9} \right) : \frac{3}{5} = \left( \frac{3}{8} - \frac{4}{9} \right) : \frac{3}{5} = \left( \frac{27 - 32}{72} \right) : \frac{3}{5} = \frac{-5}{72} : \frac{3}{5} = \frac{-5}{72} \cdot \frac{5}{3} = \frac{-25}{216}\)
- \(\text{б}) \ \frac{1}{2} \cdot \frac{8}{3} - \frac{4}{9} = \frac{8}{6} - \frac{4}{9} = \frac{4}{3} - \frac{4}{9} = \frac{12 - 4}{9} = \frac{8}{9}\)
- \(\text{в}) \ \frac{7}{5} : \left( \frac{9}{10} - \frac{2}{5} \cdot \frac{8}{9} \right) = \frac{7}{5} : \left( \frac{9}{10} - \frac{16}{45} \right) = \frac{7}{5} : \left( \frac{81 - 32}{90} \right) = \frac{7}{5} : \frac{49}{90} = \frac{7}{5} \cdot \frac{90}{49} = \frac{1}{1} \cdot \frac{18}{7} = \frac{18}{7}\)
Ответ: \(\text{а}) \ \frac{-25}{216}\); \(\text{б}) \ \frac{8}{9}\); \(\text{в}) \ \frac{18}{7}\).