Найди четыре дроби, каждая из которых больше 4/7 и меньше 6/7.

\[\frac{4}{7} < x < \frac{6}{7}\]

\[\frac{4}{7} \cdot \frac{3}{3} = \frac{12}{21};\ \ \ \ \ \ \ \frac{6}{7} \cdot \frac{3}{3} = \frac{18}{21}\]

\[\frac{12}{21} < x < \frac{18}{21}\]

\[x = \left\{ \frac{13}{21};\ \ \frac{14}{21};\ \ \frac{15}{21};\ \ \frac{16}{21} \right\}.\]

\[Ответ:\ \frac{13}{21};\ \ \frac{14}{21};\ \ \frac{15}{21};\ \ \frac{16}{21}.\]