There are 55 students in a class, 32 students in the sports team, 27 students in the art team, and each person participates in at least one team. How many people in this class participate in both teams?
一个班有学生55人，参加体育队的有32人，参加文艺队有27人，每人至少参加一个队，这个班两队都参加的有多少人．
<gadget id="calculator">27 - 55</gadget>
<output>-28</output>

<gadget id="calculator">32 + (-28)</gadget>
<output>4</output>

<result>4</result>