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}; e) 10 + (-\frac{8}{13}); ж) 8\frac{2}{7} + (-\frac{5}{14}); з) -9\frac{1}{7} + 8,5.

Решение: a) \frac{3}{7} + \frac{6}{7} = \frac{3+6}{7} = \frac{9}{7} = 1\frac{2}{7} б) -\frac{5}{11} + \frac{3}{11} = \frac{-5+3}{11} = \frac{-2}{11} = -\frac{2}{11} в) \frac{3}{4} + (-\frac{1}{6}) = \frac{3}{4} - \frac{1}{6} = \frac{9}{12} - \frac{2}{12} = \frac{7}{12} г) -1 + \frac{4}{7} = -\frac{7}{7} + \frac{4}{7} = \frac{-7+4}{7} = -\frac{3}{7} д) -4 + 2\frac{7}{8} = -4 + \frac{23}{8} = -\frac{32}{8} + \frac{23}{8} = \frac{-32+23}{8} = -\frac{9}{8} = -1\frac{1}{8} e) 10 + (-\frac{8}{13}) = 10 - \frac{8}{13} = \frac{130}{13} - \frac{8}{13} = \frac{122}{13} = 9\frac{5}{13} ж) 8\frac{2}{7} + (-\frac{5}{14}) = \frac{58}{7} - \frac{5}{14} = \frac{116}{14} - \frac{5}{14} = \frac{111}{14} = 7\frac{13}{14} з) -9\frac{1}{7} + 8,5 = -9\frac{1}{7} + 8\frac{1}{2} = -\frac{64}{7} + \frac{17}{2} = -\frac{128}{14} + \frac{119}{14} = -\frac{9}{14} Ответ: a) 1\frac{2}{7}, б) -\frac{2}{11}, в) \frac{7}{12}, г) -\frac{3}{7}, д) -1\frac{1}{8}, e) 9\frac{5}{13}, ж) 7\frac{13}{14}, з) -\frac{9}{14}