There are 20 questions in a math competition, 6 points are awarded for each correct answer, and 4 points are deducted for each wrong answer. Xiao Ming answered all the questions but got 0 points, so how many questions did he answer correctly?
一次数学竞赛共20道题目，每答对一道题得6分，每答错一道题倒扣4分．小明答完了全部的题目却得到了0分，那么他答对了多少道题．
<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<gadget id="calculator">80 + 0</gadget>
<output>80</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">80 / 10</gadget>
<output>8</output>

<result>8</result>