б) \( \frac{5}{7}y + \frac{2}{3}y - 4 = \frac{1}{7} \)

Решение:

1. \( \frac{5}{7}y + \frac{2}{3}y = 4 + \frac{1}{7} \)
2. \( \frac{15+14}{21}y = \frac{28+1}{7} \)
3. \( \frac{29}{21}y = \frac{29}{7} \)
4. \( y = \frac{29}{7} \cdot \frac{21}{29} \)
5. \( y = 3 \)

Ответ: \( y = 3 \).