In the mid-term exam, 28 people in our class were excellent in Chinese and 25 people were excellent in mathematics. How many of the 35 students in the class are excellent in both subjects?
期中考试中，我们班语文优秀的有28人，数学优秀的有25人．全班共有的35人中两门都优秀的有多少人？
<gadget id="calculator">25 - 35</gadget>
<output>-10</output>

<gadget id="calculator">28 + (-10)</gadget>
<output>18</output>

<result>18</result>