\[\boxed{\text{5.175.}}\]
\[\textbf{а)}\ \frac{15}{17} - \frac{7}{17} + \frac{2}{17} = \frac{15 - 7 + 2}{17} =\]
\[= \frac{8 + 2}{17} = \frac{10}{17}\ \]
\[\textbf{б)}\ \frac{3}{9} + \frac{5}{9} - \frac{4}{9} = \frac{3 + 5 - 4}{9} =\]
\[= \frac{8 - 4}{9} = \frac{4}{9}\ \]
\[\textbf{в)}\ \frac{10}{13} - \frac{3}{13} - \frac{2}{13} = \frac{10 - 3 - 2}{13} =\]
\[= \frac{7 - 2}{13} = \frac{5}{13}\ \]
\[\textbf{г)}\ \frac{7}{14} + \frac{2}{14} + \frac{3}{14} = \frac{7 + 2 + 3}{14} =\]
\[= \frac{9 + 3}{14} = \frac{12}{14}\ \]
\[\textbf{д)}\ \frac{15}{17} - \left( \frac{8}{17} + \frac{7}{17} \right) =\]
\[= \frac{15}{17} - \frac{8 + 7}{17} = \frac{15}{17} - \frac{15}{17} = 0\ \]
\[\textbf{е)}\ \frac{15}{18} - \left( \frac{15}{18} + \frac{5}{18} \right) =\]
\[= \frac{15}{18} - \frac{15 + 5}{18} = \frac{15}{18} - \frac{20}{18}\]
\[(В\ последнем\ примере\ \]
\[опечатка,\ дети\ еще\ \]
\[не\ проходили\ отрицательные\ \]
\[числа).\]