Решение:
а) $\frac{1}{3} - \frac{2}{3} = \frac{-(2 - 1)}{3} = \frac{-1}{3} = -\frac{1}{3};$
б) $\frac{1}{4} - \frac{3}{4} = \frac{-(3 - 1)}{4} = \frac{-2}{4} = -\frac{1}{2};$
в) $\frac{2}{7} - \frac{5}{7} = \frac{-(5 - 2)}{7} = \frac{-3}{7} = -\frac{3}{7};$
г) $\frac{7}{12} - \frac{11}{12} = \frac{-(11 - 7)}{12} = \frac{-4}{12} = -\frac{1}{3};$
д) $\frac{-8}{11} - \frac{3}{11} = \frac{-(8 + 3)}{11} = \frac{-11}{11} = -1;$
е) $-\frac{5}{17} - \frac{10}{17} = \frac{-(5 + 10)}{17} = \frac{-15}{17} = -\frac{15}{17}.$
Ответ:
а) $-\frac{1}{3};$
б) $-\frac{1}{2};$
в) $-\frac{3}{7};$
г) $-\frac{1}{3};$
д) −1;
е) $-\frac{15}{17}.$