г) \((\frac{5}{7}-\frac{3}{14})+(\frac{25}{28}-\frac{9}{14}).\)

г) \((\frac{5}{7}-\frac{3}{14})+(\frac{25}{28}-\frac{9}{14}) = (\frac{5 \cdot 2}{7 \cdot 2}-\frac{3}{14})+(\frac{25}{28}-\frac{9 \cdot 2}{14 \cdot 2}) = (\frac{10}{14}-\frac{3}{14})+(\frac{25}{28}-\frac{18}{28}) = \frac{7}{14} + \frac{7}{28} = \frac{1}{2} + \frac{1}{4} = \frac{1 \cdot 2}{2 \cdot 2} + \frac{1}{4} = \frac{2}{4} + \frac{1}{4} = \frac{2+1}{4} = \frac{3}{4}\)

Ответ: \(\frac{3}{4}\)