There are 45 students in Class 2 and 3, 25 of them participated in the painting group, and 30 participated in the calligraphy group. It is known that each student has participated in at least one group. Do you know how many people are in both groups?
二3班有45名同学，其中25人参加了绘画小组，30人参加了书法小组，已知每位同学至少参加了一个小组．你知道两个小组都参加的有多少人吗？
<gadget id="calculator">55 - 45</gadget>
<output>10</output>

<result>10</result>