The school set up two interest groups. 50 people from Class 3 and Class 1 signed up to participate in the activity. Among them, 27 people participated in the calligraphy and painting group, and 32 people participated in the chess group. How many people participated in both groups?
学校开设两个兴趣小组，三1班50人都报名参加了活动，其中27人参加书画小组，32人参加棋艺小组，两个小组都参加的有多少人
<gadget id="calculator">32 - 50</gadget>
<output>-18</output>

<gadget id="calculator">27 + (-18)</gadget>
<output>9</output>

<result>9</result>