Final answer:
The value of x that satisfies the equation f(x)=-12 is 8.
Step-by-step explanation:
To find the value of x that satisfies the equation f(x) = -12, we can substitute the equation for f(x) into -12. This gives us:
12 - 3x = -12
Solving for x:
12 - 3x + 3x = -12 + 3x
12 = -12 + 3x
24 = 3x
x = 8
Therefore, the value of x that satisfies the equation f(x) = -12 is 8.