ANSWER: -12a - 9b
Step-by-step explanation:
The problem is -9(a+b)-3a
First you have to distribute -9 to a and b which will give you -9a - 9b - 3a
Because the term -9a and -3a share the same variable you combine like terms.
-9 - 3 = -12
You will then have -12a - 9b