There are 46 students in class 31, half of them can play table tennis, and 30 can play badminton. Every student can at least one of these sports. How many students are there in both sports?
三1班有46名同学，有一半的同学会打乒乓球，会打羽毛球的有30人，每位同学至少会其中的一种运动．两种运动都会的同学有多少人？
<gadget id="calculator">46 / 2</gadget>
<output>23</output>

<gadget id="calculator">30 - 46</gadget>
<output>-16</output>

<gadget id="calculator">23 + (-16)</gadget>
<output>7</output>

<result>7</result>