Решение:
а) $-\frac{7}{15} + \frac{2}{15} - \frac{1}{5} = \frac{-7}{15} + \frac{2}{15} - \frac{3}{15} = \frac{-7 + 2 - 3}{15} = \frac{-8}{15} = -\frac{8}{15};$
б) $-\frac{1}{6} - \frac{5}{12} - \frac{7}{24} = \frac{-4}{24} - \frac{10}{24} - \frac{7}{24} = \frac{-4 - 10 - 7}{24} = \frac{-21}{24} = -\frac{7}{8};$
в) $-\frac{3}{13} - \frac{5}{13} + \frac{3}{26} = \frac{-6}{26} - \frac{10}{26} + \frac{3}{26} = \frac{-6 - 10 + 3}{26} = \frac{-13}{26} = -\frac{-1}{2};$
г) $\frac{9}{28} - \frac{4}{7} - \frac{1}{4} = \frac{9}{28} - \frac{16}{28} - \frac{7}{28} = \frac{9 - 16 - 7}{28} = \frac{-14}{28} = -\frac{1}{2};$
д) $\frac{10}{27} - \frac{5}{18} + \frac{8}{9} = \frac{20}{54} - \frac{15}{54} + \frac{48}{54} = \frac{20 - 15 + 48}{54} = \frac{53}{54};$
е) $\frac{2}{5} + \frac{1}{6} + \frac{1}{15} = \frac{12}{30} + \frac{5}{30} + \frac{2}{30} = \frac{12 + 5 + 2}{30} = \frac{19}{30}.$
Ответ:
а) $-\frac{8}{15};$
б) $-\frac{7}{8};$
в) $-\frac{-1}{2};$
г) $-\frac{1}{2};$
д) $\frac{53}{54};$
е) $\frac{19}{30}.$