My mother gave Xiaohua 20 calculation questions. It was stipulated that 5 points would be awarded for one correct answer, and 3 points would be deducted for wrong answer or failure to do one. In the end, Xiaohua scored 84 points. Count how many questions Xiaohua got right.
妈妈给小华出了20道计算题，规定对一道得5分，错一道或者不做扣3分，最终小华得了84分，算一算小华做对了几道题．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 84</gadget>
<output>16</output>

<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">16 / 8</gadget>
<output>2</output>

<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<result>18</result>