a) \(\frac{3}{11} + \left(-\frac{7}{11}\right) = \frac{3-7}{11} = \frac{-4}{11} = -\frac{4}{11}\)
б) \(\frac{6}{13} + \left(-\frac{8}{13}\right) = \frac{6-8}{13} = \frac{-2}{13} = -\frac{2}{13}\)
в) \(\frac{8}{17} + \frac{11}{17} = \frac{8+11}{17} = \frac{19}{17}\)