\[\boxed{\text{5.281.}}\]
\[\textbf{а)}\ 4\frac{4}{7} + 12\frac{5}{7} = 16\frac{9}{7} =\]
\[= 16 + \frac{9}{7} = 16 + 1\frac{2}{7} = 17\frac{2}{7}\ \]
\[\textbf{б)}\ 9\frac{8}{15} + 6\frac{13}{15} = 15\frac{21}{15} =\]
\[= 15 + \frac{21}{15} = 15 + 1\frac{6}{15} = 16\frac{6}{15}\ \]
\[\textbf{в)}\ 5\frac{4}{7} - 1\frac{5}{7} = 4\frac{11}{7} - 1\frac{5}{7} = 3\frac{6}{7}\ \]
\[\textbf{г)}\ 4\frac{8}{15} - 2\frac{13}{15} = 3\frac{23}{15} - 2\frac{13}{15} =\]
\[= 1\frac{10}{15}\text{\ \ }\]