There are 42 students in the third grade, 21 can play chess, 6 can play both chess and Go, and 10 can neither. How many people can play Go?
三年级一共有学生42名，会下象棋的有21名，既会下象棋又会下围棋的有6名，两样棋都不会的有10名．会下围棋的多少名？
<gadget id="calculator">6 - 21 - 10</gadget>
<output>-25</output>

<gadget id="calculator">42 + (-25)</gadget>
<output>17</output>

<result>17</result>