Tính \[ \left( \frac{3}{4} - \frac{3}{7} \right) - \left( \frac{9}{13} - \frac{3}{7} \right) - \left( -\frac{1}{4} - \frac{9}{13} \right) \]

----- Nội dung ảnh -----
\[
\left( \frac{3}{4} - \frac{3}{7} \right) - \left( \frac{9}{13} - \frac{3}{7} \right) - \left( -\frac{1}{4} - \frac{9}{13} \right)
\]