There are only 25 multiple-choice questions in a math test paper. If you answer a question correctly, you get 4 points, and if you get a wrong question, you will deduct 1 point. Li Hua scored 78 points, how many questions he did not do.
一张数学试卷，只有25道选择题，做对一题得4分，做错一题倒扣1分，如果不做，不得分也不扣分．李华得了78分，他有多少题没有做．
<gadget id="calculator">25 - 2 - 20</gadget>
<output>3</output>

<result>3</result>