There are 48 people in class 31, each of whom has subscribed to one or both of the following two newspapers. There are 38 people who subscribe to "Primary School Students' Mathematics Newspaper", and 40 people who subscribe to "Primary School Students' Chinese Newspaper". How many people have ordered.
三1班共有48人，每人都订了下面两种报的一种或两种，订阅《小学生数学报》的有38人，订阅《小学生语文报》的有40人，那么两种报纸全订的有多少人．
<gadget id="calculator">40 - 48</gadget>
<output>-8</output>

<gadget id="calculator">38 + (-8)</gadget>
<output>30</output>

<result>30</result>