\[\boxed{\text{5.300.}}\]
\[\textbf{а)}\ 13\frac{8}{9} - 4 = 9\frac{8}{9}\ \]
\[\textbf{б)}\ 17\frac{5}{14} - 5\frac{3}{14} = 12\frac{2}{14}\ \]
\[\textbf{в)}\ 9\frac{5}{7} - 3\frac{6}{7} = 8\frac{12}{7} - 3\frac{6}{7} = 5\frac{6}{7}\ \]
\[\textbf{г)}\ 100 - 20\frac{3}{14} =\]
\[= 99\frac{14}{14} - 20\frac{3}{14} = 79\frac{11}{14}\ \]