\[\boxed{\text{5.279.}}\]
\[\textbf{а)}\ 20\frac{3}{4} - 17 = 3\frac{3}{4}\ \]
\[\textbf{б)}\ 13\frac{8}{11} - 5\frac{2}{11} = 8\frac{6}{11}\ \]
\[\textbf{в)}\ 34\frac{7}{15} - 34 = \frac{7}{15}\ \]
\[\textbf{г)}\ 29\frac{19}{23} - 7\frac{6}{23} = 22\frac{3}{23}\ \]