When conducting a quiz, it is stipulated that each person will be given 50 points for the bottom score, and each person must answer 10 questions, and it is stipulated that 10 points will be awarded for a correct answer, and 5 points will be deducted for wrong answers or no answers. Someone scored 90 points, how many questions did this person answer correctly?
在进行智力竞赛时，规定每人底分先给50分，每人必须回答10个问题，且规定答对一题得10分，答错或不答反扣5分．某人得分90分，问这个人答对几道题？
<gadget id="calculator">90 - 50</gadget>
<output>40</output>

<gadget id="calculator">100 - 40</gadget>
<output>60</output>

<gadget id="calculator">60 / 15</gadget>
<output>4</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<result>6</result>