Xiao Ming calculates 20 questions, and stipulates that if he gets a question right, he will get 5 points, and if he gets a wrong question, 3 points will be deducted. As a result, Xiao Ming did all 20 questions, but only scored 60 points. Ask him how many questions he got right.
小明计算20道题目，规定做对一道题得5分，做错一道题反扣3分．结果小明20道题都做，却只得了60分，问他做对了多少题．
<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>