(-9b^9-11n) - (6b^9-7n) in its simplest terms

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