Bar graphs

Check the key first, every time. Here one square is one vote, so counting is enough — but that is a fact to check, not to assume.

So the counts read straight off: Football 2, Swimming 6, Running 8, Cycling 7.

Now the question, on the NUMBERS rather than the marks: Swimming is 8 − 6 = 2 fewer than Running. So the answer is 2 votes.