\[3\frac{2}{9} + 6\frac{5}{7} + 4\frac{11}{13} + 4\frac{7}{9} =\]
\[= \left( 3\frac{2}{9} + 4\frac{7}{9} \right) + \left( 6\frac{5^{\backslash 13}}{7} + 4\frac{11^{\backslash 7}}{13} \right) =\]
\[= 7\frac{9}{9} + 6\frac{65}{91} + 4\frac{77}{91} =\]
\[= 8 + 10\frac{142}{91} = 18\ \frac{142}{91} = 19\frac{51}{91}\]