Hi there! :)
Answer:

<u><em>*THE ANSWER MUST HAVE A NEGATIVE SIGN!*</em></u>
Step-by-step explanation:
First, you subtract by 8 from both sides of an equation.
5x+8-8=9x+12-8
Subtract.
12-8=4
5x=9x+4
Then, you subtract by 9x from both sides of an equation.
5x-9x=9x+4-9x
Simplify by equation.
-4x=-4
Divide by -4 from both sides of an equation.
-4x/-4=-4/-4
Divide by the numbers from left/right.
-4/-4=-1
, <em>is the FINAL/CORRECT ANSWER! :)</em>
<em>Have a nice day! :)</em>
<em>:D</em>
<em>-Charlie</em>
<em>Thank you!</em>