\[\boxed{\text{4.\ 234}}\]
\[\textbf{а)} - 2\frac{5}{8} - \frac{1}{4} = - \left( 2\frac{5}{8} + \frac{2}{8} \right) =\]
\[= - 2\frac{7}{8}\]
\[\textbf{б)}\ \frac{3}{8} - 1\frac{1}{4} = - \left( 1\frac{2}{8} - \frac{3}{8} \right) =\]
\[= - \left( \frac{10}{8} - \frac{3}{8} \right) = - \frac{7}{8}\]
\[\textbf{в)}\ 1\frac{3}{5} - \left( - 2\frac{1}{6} \right) = 1\frac{18}{30} + 2\frac{5}{30} =\]
\[= 3\frac{23}{30}\]
\[\textbf{г)} - 3\frac{7}{12} - \left( - 1\frac{3}{8} \right) =\]
\[= - 3\frac{14}{24} + 1\frac{9}{24} = - 2\frac{5}{24}\]
\[\textbf{д)} - 3\frac{1}{4} - 0,75 =\]
\[= - 3,25 - 0,75 = - 4\]
\[\textbf{е)} - 2,4 - \left( - 1\frac{1}{3} \right) =\]
\[= - 2\frac{2}{5} + 1\frac{1}{3} =\]
\[= - \left( 2\frac{6}{15} - 1\frac{5}{15} \right) = - 1\frac{1}{15}\]
\[\textbf{ж)}\ 3\frac{2}{11} - 4\frac{7}{33} =\]
\[= - \left( 4\frac{7}{33} - 3\frac{6}{33} \right) = - 1\frac{1}{33}\]
\[\textbf{з)} - 4\frac{4}{9} - \left( - 3\frac{5}{6} \right) =\]
\[= - 4\frac{8}{18} + 3\frac{15}{18} =\]
\[= - \left( 3\frac{26}{18} - 3\frac{15}{18} \right) = - \frac{11}{18}\]