\[\boxed{\mathbf{2.}\mathbf{203}}\]
\[\textbf{а)}\ \left( \frac{2^{\backslash 4}}{5} - \frac{1^{\backslash 5}}{4} \right) + \frac{9}{20} =\]
\[= \frac{8}{20} - \frac{5}{20} + \frac{9}{20} = \frac{12}{20} = \frac{3}{5}\]
\[\textbf{б)}\frac{7}{30} + \left( \frac{3^{\backslash 6}}{5} - \frac{1^{\backslash 5}}{6} \right) =\]
\[= \frac{7}{30} + \frac{18}{30} - \frac{5}{30} = \frac{20}{30} = \frac{2}{3}\]
\[\textbf{в)}\ \frac{7}{8} - \left( \frac{1}{9} + \frac{2^{\backslash 3}}{3} \right) =\]
\[= \frac{7}{8} - \left( \frac{1}{9} + \frac{6}{9} \right) = \frac{7^{\backslash 9}}{8} - \frac{7^{\backslash 8}}{9} =\]
\[= \frac{63}{72} - \frac{56}{72} = \frac{7}{72}\]
\[\textbf{г)}\ \left( \frac{5^{\backslash 5}}{14} + \frac{9^{\backslash 7}}{10} \right) - \frac{5^{\backslash 10}}{7} =\]
\[= \frac{25}{70} + \frac{63}{70} - \frac{50}{70} = \frac{38}{70} = \frac{19}{35}\]