Method 1 (Arithmetic Method): Assuming that right and wrong are equally divided, you can get 3 points for every two questions. It takes 24 questions to score according to the questions, but it exceeds the total number of questions by 4 questions. So the wrong question is 4(=24-20) and the right question is 16(=20-4).

Method 2 (Equation Solution): If you do the right question X, you will do the wrong question (20-y), which means:

5x-2(20-x)=72，x= 16。 Wrong question: 20- 16=4. For reference.