The factory has to process a total of 900 sets of cotton-padded clothes. It has been processed for 5 days, with an average of 128 sets processed per day. How many sets are left unprocessed?
工厂一共要加工900套棉衣，已经加工了5天，平均每天加工128套，还剩下多少套没有加工？
<gadget id="calculator">128 * 5</gadget>
<output>640</output>

<gadget id="calculator">900 - 640</gadget>
<output>260</output>

<result>260</result>