Xiao Ming participated in the math test, with a total of 20 questions. 5 points for a correct answer and 3 points for an incorrect answer, resulting in 60 points. How many questions did Xiao Ming get wrong? (solution by equation)
小明参加数学测试，共有20题．做对一题得5分，做错一题扣3分，结果取得60分．小明做错了几题？(用方程解)
<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>

<result>5</result>