\[\boxed{\mathbf{721\ (721).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[\textbf{а)}\frac{7}{8};\ \frac{3}{4};\ \frac{1}{3};\ \frac{1}{5}.\]
\[\textbf{б)}\frac{7}{11};\ \frac{5}{8};\ \frac{5}{12};\ \frac{1}{15}.\]
\[\textbf{в)}\frac{7}{5};\ \frac{8}{9};\ \frac{5}{7};\ \frac{3}{8}.\]
\[\textbf{г)}\ \frac{6}{5};\ \frac{8}{9};\ \frac{4}{9};\ \frac{3}{8}.\]