There are 56 students in a class, 28 students participated in the mathematics competition, 27 students participated in the Chinese competition, 16 students participated in both, how many students did not participate in both?
一个班有56人，参加数学竞赛的有28人，参加语文竞赛的有27人，两项都参加的有16人，问两项都不参加的有多少人？
<gadget id="calculator">28 - 16</gadget>
<output>12</output>

<gadget id="calculator">27 + 12</gadget>
<output>39</output>

<gadget id="calculator">56 - 39</gadget>
<output>17</output>

<result>17</result>