A total of 30 students participated in Chinese and mathematics extracurricular activities. There are 24 people participating in Chinese extracurricular activities and 26 people participating in mathematics extracurricular activities. How many people participate in both activities?
同学们参加语文与数学课外活动的一共有30人．参加语文课外活动的有24人，参加数学课外活动的有26人，则两种活动都参加的有多少人？
<gadget id="calculator">26 - 30</gadget>
<output>-4</output>

<gadget id="calculator">24 + (-4)</gadget>
<output>20</output>

<result>20</result>