15 1 1 8) - (+)

\(
\begin{aligned}
&8) \frac{15}{17} - \left(\frac{1}{5} + \frac{1}{6}\right) = \frac{15}{17} - \left(\frac{1 \cdot 6}{5 \cdot 6} + \frac{1 \cdot 5}{6 \cdot 5}\right) = \frac{15}{17} - \left(\frac{6}{30} + \frac{5}{30}\right) = \frac{15}{17} - \frac{11}{30} = \frac{15 \cdot 30}{17 \cdot 30} - \frac{11 \cdot 17}{30 \cdot 17} = \frac{450}{510} - \frac{187}{510} = \frac{263}{510}
\end{aligned}
\)