Answer:
You can see the side conditions for the function. We read the x can't be 4.
We evaluate the bottom piece at x = 4.
f(x) = -2x
Let x be 4.
f(4) = -2(4)
f(4) = -8
What about the other piece?
Evaluate the top piece at x = 2.
f(x) = 3x
Let x be 2.
f(2) = 3(2)
f(2) = 6
Answer: Choice D
Did you follow? It is a piecewise function. Solve it one piece at a time keeping each side condition in mind along the way.