There are 42 students in Class 51, 21 students can play chess, 17 students can play Go, and 10 students can't play both kinds of chess. How many students can play both kinds of chess?
五1班有42名同学，会下象棋的有21名同学，会下围棋的有17名同学，两种棋都不会下的有10名同学．两种棋都会下的有多少名同学？
<gadget id="calculator">10 - 42</gadget>
<output>-32</output>

<gadget id="calculator">21 + 17 + (-32)</gadget>
<output>6</output>

<result>6</result>