Ineed with this question i don't understand it

4 is the answer because all you have to do is replace fx with 6 and multiply -2 by the x and have six. Does that answer your question?

The answer is number four. How you do it is you plug the numbers in the x column, in your equation f(x)= -2x + 6. So for the first one in number four it would be f(6)= -2(0) + 6. when you multiply -2 and 0 you get 0, then you add 6 to that.