Right is 4 points, wrong is -4 points, and the difference between right and wrong is 4-(-4)=8 points, so assuming Xiaohua is right, she should get 80 points, and now she gets 56 points, then the difference in the middle is 80-56=24 points, that is to say, we regard 24/8=3 wrong questions as right.

So he got 20-3= 17 right and 3 wrong.