Yucai Primary School held a mathematics competition, with a total of 20 questions. The scoring standard is 5 points for a correct answer, and 2 points will be deducted for a wrong answer or a non-answer question. Xiaohong scored 79 points. She answered correctly How many questions.
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，做错一题或不答一题不但得不到分还要扣2分，小红得了79分，她答对了多少题．
<gadget id="calculator">5 * 20</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>