\[\boxed{\text{5.199.}}\]
\[\textbf{а)}\ \frac{3}{13} + \frac{5}{13} = \frac{3 + 5}{13} = \frac{8}{13}\ \]
\[\textbf{б)}\ \frac{1}{6} + \frac{4}{6} = \frac{1 + 4}{6} = \frac{5}{6}\ \]
\[\textbf{в)}\ \frac{6}{17} - \frac{3}{17} = \frac{6 - 3}{17} = \frac{3}{17}\ \]
\[\textbf{г)}\ \frac{13}{35} - \frac{7}{35} = \frac{13 - 7}{35} = \frac{6}{35}\text{\ \ }\]