x =7
Step-by-step explanation:
3x - 9 + 12 - 6x = -18
Combine like terms
-3x +3 = -18
Subtract 3 from each side
-3x +3 -3 = -18 -3
-3x = -21
Divide each side by-3
-3x /-3 = -21 /-3