Respuesta :

Answer:

  -2

Step-by-step explanation:

Put the given value in the equation and solve for x.

  f(x) = 12

  f(x) = 2(x +8)

  12 = 2(x +8) . . . . . use 12 for f(x)

  6 = x +8 . . . . . . . . divide by 2

  -2 = x . . . . . . . . . . subtract 8