12. (x - 107) : 23 = 124

Решение:

1. \[ (x - 107) : 23 = 124 \]
2. \[ x - 107 = 124 \times 23 \]
3. \[ x - 107 = 2852 \]
4. \[ x = 2852 + 107 \]
5. \[ x = 2959 \]

Ответ: x = 2959