Respuesta :

Answer:

-13x + 21

Step-by-step explanation:

12+5x-18x+9

Like terms: 5x, -18x and 12, 9

Add like terms: 5x + -18x = -13x, 12 + 9 = 21

12 + 5x - 18x + 9 = -13x + 21

I hope this helps :D
12 -13x +9=0
-13x=-12-9
-13x=-21
13x=21
X=21/13