в) \( n + \frac{5}{14}n = \frac{1}{7} \)

Решение:

1. \( n(1 + \frac{5}{14}) = \frac{1}{7} \)
2. \( n(\frac{14+5}{14}) = \frac{1}{7} \)
3. \( n(\frac{19}{14}) = \frac{1}{7} \)
4. \( n = \frac{1}{7} \cdot \frac{14}{19} \)
5. \( n = \frac{2}{19} \)

Ответ: \( n = \frac{2}{19} \).