Knowledge contest, a total of 20 questions. 6 points for a correct answer, 3 points for a wrong answer, 0 points for no answer, 102 points for Xiaoliang, how many questions he answered correctly.
知识竞赛，一共20题．答对一题得6分，答错一题扣3分，没答得0分，小亮得了102分，他答对了多少题．
<gadget id="calculator">20 * 6</gadget>
<output>120</output>

<gadget id="calculator">120 - 102</gadget>
<output>18</output>

<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">18 / 9</gadget>
<output>2</output>

<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<result>18</result>