Xiaoqiang calculated 20 competition questions, and got 5 points if he answered one question correctly, and 3 points were deducted for each question if he got it wrong or did not answer it. As a result, Xiaoqiang got 60 points. How many questions did he get right?
小强计算20道竞赛题，做对一道题得5分，做错或不做，一道题倒扣3分，结果小强得了60分．他做对了几道题？
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 60</gadget>
<output>40</output>

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

<gadget id="calculator">40 / 8</gadget>
<output>5</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<result>15</result>