The school buys chalks, white chalks are 42 boxes more than colored chalks, and colored chalks are 39 boxes, how many boxes of white chalks did you buy?
学校买粉笔，白粉笔比彩色粉笔多42盒，彩色粉笔39盒，买了多少盒白粉笔？
<gadget id="calculator">42 + 39</gadget>
<output>81</output>

<result>81</result>