\[\boxed{\text{1113.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ \frac{5}{7} > \frac{4}{9}\]
\[\frac{5}{7} > \frac{1}{2};\ \ \frac{4}{9} < \frac{1}{2}.\]
\[\textbf{б)}\ \frac{38}{39} = \frac{152}{156} > \frac{11}{12} = \frac{143}{156}\]
\[\textbf{в)}\ 3,12 < 3\frac{1}{8} = 3,125\]
\[\textbf{г)}\ 17,2(7) > 17,27\]