Zhenhai Yale School held a health knowledge competition. There were 20 questions in total. One correct answer was worth 10 points, and one wrong answer was 10 points deducted. Little Swallow participated in this competition and got 100 points. How many questions did Little Swallow answer correctly?
镇海雅乐学校举行卫生常识知识竞赛，共有20道题，答对一道题得10分，答错一道题要扣10分，小燕子参加这次竞赛得了100分，小燕子答对了多少道题．
<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<gadget id="calculator">200 - 100</gadget>
<output>100</output>

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<result>15</result>