First, I'd like to state there are many possibilties to for this solution.
Okay, 9/3 + 3 = -1b
Lets check.
PEMDAS!
9/3 is = 3
So:
3 + 3 = -1b
Then combine like terms:
6 = -1b
Following PEMDAS, divide -1 on both sides so..
-6 = b or b = -6
So, 9/3 + 3 = -1b works!!!