The fourth-grade students of Guangming Primary School held a quiz competition. To encourage everyone to rush to answer, it was stipulated that 10 points would be awarded for each correct answer, and 5 points would be deducted for each wrong answer. Class 4 students answered 10 times and scored 40 points in total. How many questions did they get right?
光明小学四年级学生举行智力竞赛，为鼓励大家抢答，规定答对一题加10分，答错一题扣5分．四1班同学抢答到10次，共得40分．他们答对了多少道？
<gadget id="calculator">10 * 10</gadget>
<output>100</output>

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

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

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

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

<result>6</result>