\[ \frac{3}{4} - \frac{5}{7} = \frac{3 \times 7 - 5 \times 4}{4 \times 7} = \frac{21 - 20}{28} = \frac{1}{28} \]
\[ \frac{5}{14} : \frac{1}{28} = \frac{5}{14} \times \frac{28}{1} = \frac{5 \times 28}{14} \]
\[ \frac{5 \times 2 \times 14}{14} = 5 \times 2 = 10 \]
Ответ: 10