The expression you provided is the sum of two complex numbers: $(3 + 4i) + (9 - 3i)$.

To add these complex numbers, combine the real parts and the imaginary parts separately:

$(3 + 9) + (4i - 3i) = 12 + 1i$

So, the result is:

$12 + i$

Would you like more details or have any questions?

Here are some related questions for further exploration:

1. What is the result of subtracting $(9 - 3i)$ from $(3 + 4i)$?
2. How do you multiply two complex numbers like $(3 + 4i)(9 - 3i)$?
3. What is the magnitude of the complex number $12 + i$?
4. How can you graph the complex number $12 + i$ on the complex plane?
5. How do you find the conjugate of a complex number?

Tip: When adding or subtracting complex numbers, always handle real and imaginary parts separately.