a) $$\frac{15}{17} - \frac{7}{17} + \frac{2}{17} = \frac{15-7+2}{17} = \frac{10}{17}$$
б) $$\frac{3}{9} + \frac{5}{9} - \frac{4}{9} = \frac{3+5-4}{9} = \frac{4}{9}$$
в) $$\frac{10}{13} - \frac{3}{13} - \frac{2}{13} = \frac{10-3-2}{13} = \frac{5}{13}$$
Ответ: a) $$\frac{10}{17}$$, б) $$\frac{4}{9}$$, в) $$\frac{5}{13}$$