Verified Answer :

The answer is 
y= - x-9/3 I believe.
1- Subtract 9 from both sides.
-3y = x - 9
2- Divide both sides by -3
y = - x-9/3

Simplifying
9 + -3y = x

 9 + -3y = x
 9 + -9 + -3y = -9 + x

 9 + -9 = 0
0 + -3y = -9 + x
-3y = -9 + x

'-3' y=-3 + -0.3333333333x
i hope this helped you out!