4.221 Выполните сложение: a) -\frac{3}{7} + \frac{6}{7}; б) -\frac{5}{11} + \frac{3}{11}; в) \frac{3}{4} + (-\frac{1}{6}); г) -1+\frac{4}{7}; д) -4 + 2\frac{7}{8}; ж) 8\frac{2}{7}+(-7\frac{5}{14}); e) 10+(-8\frac{5}{13}); з) -9\frac{1}{7} + 8,5.

\[-\frac{3}{7} + \frac{6}{7} = \frac{6-3}{7} = \frac{3}{7}\]

\[-\frac{5}{11} + \frac{3}{11} = \frac{3-5}{11} = -\frac{2}{11}\]

\[\frac{3}{4} + (-\frac{1}{6}) = \frac{3}{4} - \frac{1}{6} = \frac{9}{12} - \frac{2}{12} = \frac{7}{12}\]

\[-1+\frac{4}{7} = -\frac{7}{7} + \frac{4}{7} = \frac{4-7}{7} = -\frac{3}{7}\]

\[-4 + 2\frac{7}{8} = -4 + \frac{23}{8} = -\frac{32}{8} + \frac{23}{8} = \frac{23-32}{8} = -\frac{9}{8} = -1\frac{1}{8}\]

\[8\frac{2}{7}+(-7\frac{5}{14}) = 8\frac{4}{14} - 7\frac{5}{14} = 1\frac{4}{14} - \frac{5}{14} = \frac{18}{14} - \frac{5}{14} = \frac{13}{14}\]

\[10+(-8\frac{5}{13}) = 10 - 8\frac{5}{13} = 10 - \frac{109}{13} = \frac{130}{13} - \frac{109}{13} = \frac{21}{13} = 1\frac{8}{13}\]

\[-9\frac{1}{7} + 8,5 = -9\frac{1}{7} + 8\frac{1}{2} = -9\frac{2}{14} + 8\frac{7}{14} = -\frac{128}{14} + \frac{119}{14} = -\frac{9}{14}\]