\[\boxed{\mathbf{2.}\mathbf{173}}\]
\[\textbf{а)}\ \frac{23}{24} - \left( \frac{1^{\backslash 4}}{6} + \frac{1^{\backslash 6}}{4} \right) =\]
\[= \frac{23}{24} - \left( \frac{4}{24} + \frac{6}{24} \right) =\]
\[= \frac{23}{24} - \frac{10}{24} = \frac{13}{24}\]
\[\textbf{б)}\ \frac{4}{35} + \left( \frac{3^{\backslash 7}}{5} - \frac{4^{\backslash 5}}{7} \right) =\]
\[= \frac{4}{35} + \left( \frac{21}{35} - \frac{20}{35} \right) = \frac{4}{35} + \frac{1}{35} =\]
\[= \frac{5}{35} = \frac{1}{7}\]
\[\textbf{в)}\ \frac{11}{15} - \left( \frac{2^{\backslash 20}}{3} - \frac{3^{\backslash 3}}{20} \right) =\]
\[= \frac{44}{60} - \left( \frac{40}{60} - \frac{9}{60} \right) = \frac{44}{60} - \frac{31}{60} =\]
\[= \frac{13}{60}\]
\[\textbf{г)}\ \frac{5}{18} + \left( \frac{2^{\backslash 3}}{9} + \frac{1}{27} \right) =\]
\[= \frac{15}{54} + \left( \frac{12}{54} + \frac{2}{54} \right) = \frac{15}{54} + \frac{14}{54} =\]
\[= \frac{29}{54}\]