algebra
posted by mike .
use the graph of the function f to find f(4), f(3), and f(2)

We do not see the graph, so we're unable to find f(4), etc.
On the other hand, with the graph in hand, you could look up 4 in the xaxis, go vertically until you hit the curve then go horizontally to find the corresponding value for y, which equals f(4) in this case.