\[\boxed{\text{4.\ 308}}\]
\[\textbf{а)} - 1\ :( - 8) = \frac{1}{8}\]
\[\textbf{б)} - 1\ :5 = - \frac{1}{5}\]
\[\textbf{в)}\ 1\ :( - 4) = - \frac{1}{4}\]
\[\textbf{г)} - 7\ :( - 2) = \frac{7}{2} = 3,5\]
\[\textbf{д)} - 9\ :10 = - \frac{9}{10} = - 0,9\]
\[\textbf{е)}\ 23\ :( - 9) = - \frac{23}{9} = - 2\frac{5}{9}\]