Class 4 has a number of exercise books to distribute to the students. If each person distributes 5 books, there are 7 books left; if each person sends 7 books, there are still 5 books left. How many students are there?
四1班有若干本练习本要发给同学们．若每人发5本，还剩7本；每人发7本，则还差5本，有几名同学？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

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

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<result>6</result>