There are 15 questions in an intelligence test. For every correct answer, 3 points will be awarded, and 2 points will be deducted for every wrong answer. Xiao Ming gets 30 points after answering 15 questions. How many questions did he get right?
一次智力测试有15题，每答对一题得3分，答错一题反扣2分，小明答完15题得了30分，他做对了多少题．
<gadget id="calculator">3 * 15</gadget>
<output>45</output>

<gadget id="calculator">45 - 30</gadget>
<output>15</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>