There are 55 people in the science and technology activity group. In a timed scientific and technological activity competition for making airplane models and ship models, the teacher counted and found that: 40 students made a model airplane and 32 students made a ship. Every student has completed at least one production. Ask how many students have completed both productions.
科技活动小组有55人．在一次制作飞机模型和制作舰艇模型的定时科技活动比赛中，老师到时清点发现：制作好一架飞机模型的同学有40人，制作好一艘舰艇的同学有32人．每个同学都至少完成了一项制作．问两项制作都完成的同学有多少人．
<gadget id="calculator">32 - 55</gadget>
<output>-23</output>

<gadget id="calculator">40 + (-23)</gadget>
<output>17</output>

<result>17</result>