The second class of the sixth grade held a quiz quiz. 10 points were awarded for one correct answer, and 10 points were deducted for one wrong answer. Hu Shaohong answered 9 questions and scored 30 points. How many questions did he answer correctly?
六年级二班进行智力抢答赛，答对1题得10分，答错一题扣10分，胡绍洪同学答了9个题，得了30分，他答对多少道题．
<gadget id="calculator">10 * 9</gadget>
<output>90</output>

<gadget id="calculator">90 - 30</gadget>
<output>60</output>

<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

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

<result>6</result>