Xiaohua participates in a mathematics competition. There are 20 questions in the test. The scoring standard is: 8 points for a correct answer, and 4 points for a wrong answer. Xiaohua scored 100 points in the test, how many questions did he answer correctly?
小华参加数学竞赛，试题共20道题，评分标准是：答对一题给8分，错一题倒扣4分．小华考了100分，问他答对了几道题？
<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>