Tính:
Giải thích
\[\frac{{\left( { - \frac{5}{7} - \frac{7}{9} + \frac{9}{{11}} - \frac{{11}}{{13}}} \right) \cdot \left( {3 - \frac{3}{4}} \right)}}{{\left( {\frac{{10}}{{21}} + \frac{{14}}{{27}} - \frac{{18}}{{33}} + \frac{{22}}{{39}}} \right):\left( {2 - \frac{2}{3}} \right)}}\]
\[ = \frac{{\left( { - \frac{5}{7} - \frac{7}{9} + \frac{9}{{11}} - \frac{{11}}{{13}}} \right) \cdot \frac{9}{4}}}{{ - \frac{2}{3} \cdot \left( { - \frac{5}{7} - \frac{7}{9} + \frac{9}{{11}} - \frac{{11}}{{13}}} \right) \cdot \frac{3}{4}}}\]
\[ = \frac{{\frac{9}{4}}}{{ - \frac{2}{4}}} = \frac{9}{4} \cdot \left( { - 2} \right) = - \frac{9}{2}.\]