\[Стр.\ 13.\]
\[\boxed{\mathbf{3.}}\]
\[В\ порядке\ убывания:\]
\[\frac{11}{8};\ \frac{8}{8};\ \frac{7}{8};\ \frac{5}{8};\ \frac{3}{8};\ \frac{2}{8}.\]
\[В\ порядке\ возрастания:\]
\[\frac{2}{8};\ \frac{3}{8};\ \frac{5}{8};\ \frac{7}{8};\ \frac{8}{8};\ \frac{11}{8}.\]
\[\boxed{\mathbf{4.}}\]
\[В\ порядке\ возрастания:\]
\[\frac{1}{6};\ \frac{1}{3};\ \frac{1}{2};\ \frac{5}{6};\ \frac{6}{6};\ \frac{5}{3}.\]
\[В\ порядке\ убывания:\]
\[\frac{5}{3};\ \frac{6}{6};\ \frac{5}{6};\ \frac{1}{2};\ \frac{1}{3};\ \frac{1}{6}.\]
\[\boxed{\mathbf{5.}}\]
\[В\ порядке\ возрастания:\]
\[\frac{2}{13};\ \frac{3}{13};\ \frac{5}{13};\ \frac{7}{13};\ \frac{9}{13};\ \frac{4}{4}.\]
\[\boxed{\mathbf{6.}}\]
\[В\ порядке\ убывания:\ \]
\[\frac{21}{19};\ \frac{5}{5};\ \frac{9}{19};\ \frac{7}{19};\ \frac{6}{19};\ \frac{4}{19}.\]
\[\boxed{\mathbf{7.}}\]
\[\frac{a}{17} < \frac{6}{17}\]
\[a = 1;2;3;4;5.\]
\[\frac{5}{13} > \frac{a}{13}\]
\[a = 1;2;3;4.\]
\[\frac{a}{11} < \frac{5}{11}\]
\[a = 1;2;3;4.\]
\[\frac{7}{12} > \frac{a}{12}\]
\[a = 1;2;3;4;5;6.\]