There are 45 people in the second class of four years, 18 people who can only play table tennis, 7 people who can play both table tennis and badminton, and 6 people who can't play table tennis and badminton. How many people can only play badminton? people.
四年二班有45人，只会打乒乓球的18人，乒乓球、羽毛球都会的有7人，不会打乒乓球又不会打羽毛球的有6人，问只会打羽毛球的有多少人．
<gadget id="calculator">45 - 6</gadget>
<output>39</output>

<gadget id="calculator">39 - 18 - 7</gadget>
<output>14</output>

<result>14</result>