There are 40 students in class 31, all of whom signed up for the interest group, among which 25 students participated in the language interest group, 23 students participated in the mathematics interest group, how many people participated in both interest groups.
三1班有40名同学，全部报名参加了兴趣小组，其中25名同学参加了语文兴趣小组，23名同学参加了数学兴趣小组，两个兴趣小组都参加了的有多少人．
<gadget id="calculator">23 - 40</gadget>
<output>-17</output>

<gadget id="calculator">25 + (-17)</gadget>
<output>8</output>

<result>8</result>