(5x - 7) * 5 = 15

Решение:

1. \( (5x - 7) \cdot 5 = 15 \)
2. \( 5x - 7 = \frac{15}{5} \)
3. \( 5x - 7 = 3 \)
4. \( 5x = 3 + 7 \)
5. \( 5x = 10 \)
6. \( x = \frac{10}{5} \)
7. \( x = 2 \)

Ответ: 2