Respuesta :

-x+4(x+3) = 9

Multiplying...

-x+4x+12=9
So,
3x + 12 = 9

Now, subtract 12 from both sides.

3x + 12 - 12 = 9 - 12
3x = -3

Then, divide by 3.
3x/3 = -3/3
x = -1