Answer:
You subtract 9 from both sides
Step-by-step explanation:
You have to get the variable by itself to solve so you subract 9 by 9 and they cancel each other out. Then you do -12-9 and since they are both negative you get get -21
Them you have your answer m=-21, you can check this by plugging m inot the equation
If you are solving for M
You would subtract 9
m + 9 = -12
- 9 - 9
M = -21