\[\frac{4}{15} + \frac{3}{7} + \frac{11}{15} + \frac{6}{7} =\]
\[= \left( \frac{4}{15} + \frac{11}{15} \right) + \left( \frac{3}{7} + \frac{6}{7} \right) =\]
\[= \frac{15}{15} + \frac{9}{7} = 1 + 1\frac{2}{7} = 2\frac{2}{7}\]