A batch of 900 homework books came in from the canteen, 534 of which were sold in the morning and 326 in the afternoon. How many homework books are left in this batch?
小卖部进来一批作业本共有900本，上午就卖去534本，下午又卖去326本，这批作业本还剩多少？
<gadget id="calculator">900 - 534 - 326</gadget>
<output>40</output>

<result>40</result>