\[\boxed{\mathbf{4.}\mathbf{57}}\]
\[\textbf{а)} - a = \frac{4}{7}\]
\[a = - \frac{4}{7}.\]
\[\textbf{б)}\ \ b = 9\frac{7}{9}\]
\[- b = - 9\frac{7}{9}.\]
\[\textbf{в)} - c = - 3,4\]
\[c = 3,4.\]
\[\textbf{г)}\ d = - 6\frac{5}{11}\]
\[- d = 6\frac{5}{11}.\]