\[\boxed{\text{5.484.}}\]
\[\textbf{а)}\ m + \frac{4}{7} = \frac{11}{14}\]
\[m = \frac{11}{14} - \frac{4}{7}\]
\[m = \frac{11}{14} - \frac{8}{14}\]
\[m = \frac{3}{14}.\]
\[m - \frac{4}{7} = \frac{11}{14}\]
\[m = \frac{11}{14} + \frac{4}{7}\]
\[m = \frac{11}{14} + \frac{8}{14}\]
\[m = \frac{19}{14} = 1\frac{5}{14}.\]
\[\textbf{б)}\ \frac{5}{7} - c = \frac{3}{14}\]
\[c = \frac{5}{7} - \frac{3}{14}\]
\[c = \frac{10}{14} - \frac{3}{14}\]
\[c = \frac{7}{14} = \frac{1}{2}.\]