Вычислите: 19/39+(18/39-6/39)-13/39.

\[\frac{19}{39} + \left( \frac{18}{39} - \frac{6}{39} \right) - \frac{13}{39} =\]

\[= \frac{19}{39} + \frac{12}{39} - \frac{13}{39} = \frac{18}{39} = \frac{6}{13}.\]