There are 50 workers in a workshop. The workshop organizes activities. There are 34 people participating in rowing and 28 people participating in swimming. How many people in the workshop participate in both activities.
某车间有50名工人，车间组织活动，参加划船的有34人，参加游泳的有28人，车间有多少人两项活动都参加．
<gadget id="calculator">28 - 50</gadget>
<output>-22</output>

<gadget id="calculator">34 + (-22)</gadget>
<output>12</output>

<result>12</result>