There are 50 students in a class, and each of them participates in at least one interest group. Among them, 37 students participate in the science and technology group, and 25 students participate in the composition group. Find the number of people who participate in the two interest groups at the same time as the whole class.
某班50个学生，每人至少参加一个兴趣小组，其中有37人参加科技组，25人参加作文组，求同时参加两个兴趣小组的人数相当于全班人数的多少．
<gadget id="calculator">25 - 50</gadget>
<output>-25</output>

<gadget id="calculator">37 + (-25)</gadget>
<output>12</output>

<gadget id="calculator">12 / 50</gadget>
<output>6/25 = around 0.24</output>

<result>6/25 = around 0.24</result>