-9--4

To subtract two negative numbers, you can follow these steps:

1. Start with the first negative number (-9).
2. Change the signs of both numbers (make them positive): -9 becomes +9 and -4 becomes +4.
3. Subtract the second positive number from the first positive number: 9 - 4 = 5.
4. Since the original numbers were negatives, the final answer will also be negative.
5. Add the negative sign to the result: -5.

Therefore, -9 - (-4) = -5.