The school bought 10 boxes of the same chalk, and after taking out 20 boxes from each box, the remaining quantity is exactly equal to the original 6 boxes. So, how many boxes of chalk are there in a box?
学校购买了同样的粉笔10箱，从每箱中取出20盒后，余下的恰好等于原来6箱的数量．那么，一箱有多少盒粉笔．
<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<result>50</result>