A total of 15 math exercises. 8 points are awarded for each correct answer, and 4 points are deducted for wrong answers. Xiaogang scored 84 points. How many questions did he answer correctly?
一次数学练习题共15题．每做对一题得8分，做错或不做倒扣4分，小刚得了84分，他做对了几道题？
<gadget id="calculator">15 * 8</gadget>
<output>120</output>

<gadget id="calculator">120 - 84</gadget>
<output>36</output>

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

<gadget id="calculator">36 / 12</gadget>
<output>3</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>