10. Вычислите: а) \(\frac{1}{3}+\left(-\frac{2}{7}\right)\); б) \(-\frac{4}{9}+\frac{2}{3}\); в) \(-\frac{5}{12}+\frac{7}{9}\); г) \(\frac{8}{15}+\left(-\frac{7}{10}\right)\).

1. \(\frac{1}{3}-\frac{2}{7}=\frac{7-6}{21}=\frac{1}{21}\).
2. \(-\frac{4}{9}+\frac{2}{3}=-\frac{4}{9}+\frac{6}{9}=\frac{2}{9}\).
3. \(-\frac{5}{12}+\frac{7}{9}=-\frac{15}{36}+\frac{28}{36}=\frac{13}{36}\).
4. \(\frac{8}{15}-\frac{7}{10}=\frac{16}{30}-\frac{21}{30}=-\frac{5}{30}=-\frac{1}{6}\).

Ответ: а) \(\frac{1}{21}\); б) \(\frac{2}{9}\); в) \(\frac{13}{36}\); г) \(-\frac{1}{6}\).