There are 42 students in a certain class, all of whom participated in interest groups, including 32 students who participated in mathematics and 27 students who participated in music. How many people participated in both interest groups?
某班42人，都参加了兴趣小组，其中参加数学的有32人，参加音乐的有27人．两种兴趣小组都参加的有多少人？
<gadget id="calculator">32 - 42</gadget>
<output>-10</output>

<gadget id="calculator">27 + (-10)</gadget>
<output>17</output>

<result>17</result>