There are 30 students from class 3 and 2 participating in the competition, among which 20 students participated in the mathematics competition and 16 students participated in the art competition. How many people participate in both math and art competitions?
三2班有30个学生参加竞赛，其中参加数学竞赛的有20人，参加美术竞赛的有16人．既参加数学竞赛又参加美术竞赛的有多少人？
<gadget id="calculator">16 - 30</gadget>
<output>-14</output>

<gadget id="calculator">20 + (-14)</gadget>
<output>6</output>

<result>6</result>