There are 50 people in Class 1, 39 of them can dance, 37 can play musical instruments, and 48 can play chess. If there are no ones who can do any of these three things, how many people can do all three.
六1班有50人，其中会跳舞的有39人，会乐器的有37人，会下棋的有48人，这三项一项都不会的没有，则三项都会的有多少人．
<gadget id="calculator">50 - 39</gadget>
<output>11</output>

<gadget id="calculator">50 - 37</gadget>
<output>13</output>

<gadget id="calculator">11 + 13 + 2</gadget>
<output>26</output>

<gadget id="calculator">50 - 26</gadget>
<output>24</output>

<result>24</result>