Hello, there!
In this case, we can get rid of the parenthesis
-9b^9 - 11n - 6b^9 + 7n
Now, we will simplify like terms.
-9b^9 and -6b^9 are like terms.
-9b^9 + -6b^9 = -15b^9
-11n and 7n are like terms (it is 7n because when you subtract, you switch signs.)
-11n + 7n = -4n
So, our final answer is -15b^9 - 4n
I hope I helped!
Let me know if you need anything else!
~ Zoe