In a certain elementary school mathematics competition, students had to answer 15 questions in total. 8 points are awarded for each correct answer, and 5 points are deducted for incorrect answers. A student answered 15 questions and scored 55 points in total. How many questions did he answer correctly?
在某一次小学数学竞赛里，同学总共要答15题问题．每题答对的得8分，答错的倒扣5分．某同学作答了15题共得55分，他答对了多少题？
<gadget id="calculator">15 * 5</gadget>
<output>75</output>

<gadget id="calculator">75 + 55</gadget>
<output>130</output>

<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">130 / 13</gadget>
<output>10</output>

<result>10</result>