2. Выполните действия: 1) $\frac{16}{17} - \frac{15}{17}$; 2) $\frac{8}{21} + \frac{3}{21}$; 3) $\frac{5}{26} + (\frac{11}{26} - \frac{7}{26})$; 4) $(\frac{4}{11} + \frac{6}{11}) - \frac{2}{11}$

1) $\frac{16}{17} - \frac{15}{17} = \frac{16 - 15}{17} = \frac{1}{17}$ 2) $\frac{8}{21} + \frac{3}{21} = \frac{8 + 3}{21} = \frac{11}{21}$ 3) $\frac{5}{26} + (\frac{11}{26} - \frac{7}{26}) = \frac{5}{26} + \frac{11 - 7}{26} = \frac{5}{26} + \frac{4}{26} = \frac{5 + 4}{26} = \frac{9}{26}$ 4) $(\frac{4}{11} + \frac{6}{11}) - \frac{2}{11} = \frac{4 + 6}{11} - \frac{2}{11} = \frac{10}{11} - \frac{2}{11} = \frac{10 - 2}{11} = \frac{8}{11}$