In a frequency graph, it's bad form to make the frequency the x-axis (because it's the dependent variable) which means that the frequency is the y-axis. So the answer has to be 3 They should have labelled the axes though.
The axis should be labelled, but they don't have to be labelled in order to draw a conclusion.
It only makes sense if the x-axis is the score and the y-axis is the number of students, because a longer column equates to a more frequent result. Having the x-axis be the number of students doesn't make sense because there are repeat instances (5 + 9 + 10 students getting a score of 3).
So it's either 3 (score of exactly 5) or 27 (scored at least 5).