In the children's day performance, 14 people danced and 28 people sang in chorus. A total of 35 people participated in these two performances. How many people participated in both.
儿童节文艺汇演中，跳舞的有14人，合唱的有28人，参加这两项演出的一共有35人．两项都参加的有多少人．
<gadget id="calculator">30 - 35</gadget>
<output>-5</output>

<gadget id="calculator">14 + (-5)</gadget>
<output>9</output>

<result>9</result>