There are generally 48 students in the fourth grade. After the self-study class in the afternoon, 37 people have finished their Chinese homework, 42 people have finished their math homework, and no one has finished both homework. How many people have finished their Chinese and math homework?
四年级一般有48人，下午自习课后，做完语文作业的37人，做完数学作业的有42人，没有人两科作业都没做完．语文、数学作业都做完的有多少人？
<gadget id="calculator">42 - 48</gadget>
<output>-6</output>

<gadget id="calculator">37 + (-6)</gadget>
<output>31</output>

<result>31</result>