There are 20 questions in the sixth grade calculation competition. It is stipulated that 5 points will be awarded for a correct question, and 2 points will be deducted for a wrong question. , Xiaohua scored 79 points, how many questions did he get right.
六年级进行计算比赛，共20题，规定算对一题得5分，错一题扣2分．，晓华得了79分，他做对多少题．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 79</gadget>
<output>21</output>

<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">21 / 7</gadget>
<output>3</output>

<gadget id="calculator">20 - 3</gadget>
<output>17</output>

<result>17</result>