There are 20 questions in the Mathematical Quiz Competition. If you answer a question correctly, you get 5 points, and if you answer a wrong question, 2 points are deducted. Xiao Ming scored 79 points. How many questions did Xiao Ming answer correctly?
数学智力竞赛共有20道题，答对一题得5分，答错一题扣2分，小明得了79分，小明答对了多少题？
<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>