Perform the operation

-3+(-9)

-3+(-9) is equal to -12.

To perform the operation -3 + (-9), you need to add the two numbers together.

-3 + (-9)

=(-3) + (-9)

To add two negative numbers, you can simply add their absolute values and keep the negative sign.

=(-3 - 9)

=-12

Therefore, -3 + (-9) = -12.