find the function value f(3), f(-4),and f(0) for F(X) =4 if x> or equal to 0
3 if x <0 .

So where are you stuck? It's a very simple function. If the argument is less than 0, the answer is 3; otherwise, if it's greater than or equal to 0, the answer is 4.

Is 3 less than 0? No. Then F(3) must be 4.

So how about -4? Is that less than 0 or is it greater than or equal?

How about 0?