The expression $-6 + (-3)$ can be simplified as follows:

$-6 + (-3) = -6 - 3 = -9$

Thus, the result is $-9$.

Would you like more details or have any questions about this?

Here are 5 related questions you might find helpful:

1. What is the result of $-10 + (-5)$?
2. How do you add two negative numbers?
3. What is the result of $-8 + 2$?
4. What is the absolute value of $-9$?
5. How would you subtract $-6 - (-3)$?

Tip: When adding two negative numbers, you add their absolute values and keep the negative sign.