There are a total of 20 questions in the math competition, 6 points are awarded for each correct answer, and 3 points are deducted for each wrong answer. Xiao Ming has a total of 55 points. How many questions did he get right?
数学竞赛共出了20题，做对一题得6分，做错1题倒扣3分，小明共得55分，他做对了多少题．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 55</gadget>
<output>45</output>

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

<gadget id="calculator">45 / 9</gadget>
<output>5</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<result>15</result>