25. 21-(5x+14)=2499

Решение:

1. \[ 21 - (5x + 14) = 2499 \]
2. \[ -(5x + 14) = 2499 - 21 \]
3. \[ -(5x + 14) = 2478 \]
4. \[ 5x + 14 = -2478 \]
5. \[ 5x = -2478 - 14 \]
6. \[ 5x = -2492 \]
7. \[ x = -2492 : 5 \]
8. \[ x = -498.4 \]

Ответ: x = -498.4