Dahua Garment Factory plans to make 660 sets of clothes. It has been done for 4.5 days, with an average of 72 sets per day. The rest should be done within 4 days, how many sets should be done on average per day?
大华服装厂计划做660套衣服，已经做了4.5天，平均每天做72套．剩下的要在4天里做完，平均每天应做多少套？
<gadget id="calculator">72 * 4.5</gadget>
<output>324</output>

<gadget id="calculator">660 - 324</gadget>
<output>336</output>

<gadget id="calculator">336 / 4</gadget>
<output>84</output>

<result>84</result>