In a speed calculation competition, the scores for each question are the same. Xiao Ming got 15 of the first 20 questions right, and of the remaining questions, he only got half of the questions right, and got 50 points. If the full score is 100 points, how many questions did he get right?
一次速算比赛，每道题的分数都一样．小明做对了前20题中的15题，余下的题中，他做对的题仅是做错的一半，结果得了50分，如果满分是100分，那么他做对了多少道题．
<gadget id="calculator">15 - 20</gadget>
<output>-5</output>

<gadget id="calculator">15 + (-5)</gadget>
<output>10</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">10 / 1</gadget>
<output>10</output>

<gadget id="calculator">15 + 10</gadget>
<output>25</output>

<result>25</result>