There are 20 math competition questions. 8 points are awarded for each correct answer, and 4 points are deducted for each incorrect answer. Xiaoli got 100 points, how many questions did she get right?
数学竞赛题共20道．每做对一题得8分，做错一题倒扣4分．小丽得了100分，她做对了多少道题．
<gadget id="calculator">20 * 8</gadget>
<output>160</output>

<gadget id="calculator">160 - 100</gadget>
<output>60</output>

<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">60 / 12</gadget>
<output>5</output>

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

<result>15</result>