\[\boxed{\mathbf{618\ (618)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
Пояснение.
Решение.
\[1)\ \frac{a}{39} = \frac{b}{8}\]
\[8a = 39b\]
\[\frac{a}{b} = \frac{39}{8} = 4\frac{7}{8}.\]
\[2)\ \frac{7}{a} = \frac{6}{b}\]
\[6a = 7b\]
\[\frac{a}{b} = \frac{7}{6} = 1\frac{1}{6}.\]