Xiao Ming did 20 questions and got a total of 60 points. For every question he got right, he got 4 points, and for every wrong question, 1 point was deducted. How many questions did Xiao Ming get wrong?
小明做了20道题，共得了60分，每做对一题得4分，做错一题扣1分，小明做错了多少道题．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

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

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<result>8</result>