\[\boxed{\text{6.66.}}\]
\[\textbf{а)}\ 37\frac{9}{13} - 13\frac{6}{13} + 7\frac{2}{13} =\]
\[= 24\frac{3}{13} + 7\frac{2}{13} = 31\frac{5}{13};\ \]
\[\textbf{б)}\ 21\frac{2}{9} + 4\frac{5}{6} - 5\frac{4}{9} =\]
\[= \left( 21\frac{2}{9} - 5\frac{4}{9} \right) + 4\frac{5}{6} =\]
\[= \left( 20\frac{11}{9} - 5\frac{4}{9} \right) + 4\frac{5}{6} =\]
\[= 15\frac{7}{9} + 4\frac{5}{6} = 15\frac{14}{18} + 4\frac{15}{18} =\]
\[= 19\frac{29}{18} = 20\frac{11}{18};\ \]
\[\textbf{в)}\ 54\frac{3}{11} + 8\frac{5}{11} + \frac{3}{22} =\]
\[= 54\frac{6}{22} + 8\frac{10}{22} + \frac{3}{22} =\]
\[= 62\frac{16}{22} + \frac{3}{22} = 62\frac{19}{22};\ \]
\[\textbf{г)}\ 6\frac{9}{10} + 2\frac{7}{10} + 4\frac{1}{10} =\]
\[= 8\frac{16}{10} + 4\frac{1}{10} = 9\frac{6}{10} + 4\frac{1}{10} =\]
\[= 13\frac{7}{10};\ \]
\[\textbf{д)}\ 14\frac{23}{100} - 3\frac{11}{100} - 1 =\]
\[= 11\frac{12}{100} - 1 = 10\frac{12}{100} = 10\frac{3}{25};\ \]
\[\textbf{е)}\ 10 - 5\frac{39}{100} - 2\frac{56}{100} =\]
\[= 9\frac{100}{100} - 5\frac{39}{100} - 2\frac{56}{100} =\]
\[= 4\frac{61}{100} - 2\frac{56}{100} = 2\frac{5}{100} = 2\frac{1}{20}\text{.\ \ \ }\]