This question is asking you to find the value of f(x) which is really just the y-coordinate. You need to find the y-coordinate for f(4), which means when x=4. So, go to the line on the graph where x=4 and find the point that lies there. In this case, when x=4 the y-coordinate is 2. The coordinates for this point are (4,2) and can be seen on the far right side of the graph.
