There were 20 questions in a certain mathematics competition, 5 points were awarded for 1 question correct, and 3 points were deducted for 1 question incorrectly. Li Jun did all the questions and got 68 points. How many questions did he get wrong.
某次数学竞赛共20题，做对1题得5分，做错1题倒扣3分，李军做了所有的题，得了68分．他做错了多少道题．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 68</gadget>
<output>32</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">32 / 8</gadget>
<output>4</output>

<result>4</result>