Yucai Primary School held a math competition with 20 questions in total. The scoring standard was 5 points for a correct answer and 2 points for a wrong or non-answer question. Xiaohong got 79 points. How many questions did she answer correctly?
育才小学举行数学竞赛，共20道题，评分标准是答对一题得5分，做错或不答一题扣2分，小红得了79分．她答对了多少道题．
<gadget id="calculator">5 * 20</gadget>
<output>100</output>

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

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