The factory plans to produce 1500 watches, 300 watches per day in the first 2 days, and 450 watches per day later. How many days will it take to complete the task?
工厂计划生产手表1500只，前2天每天生产300只，后来每天生产450只．还要多少天才能完成任务？
<gadget id="calculator">300 * 2</gadget>
<output>600</output>

<gadget id="calculator">1_500 - 600</gadget>
<output>900</output>

<gadget id="calculator">900 / 450</gadget>
<output>2</output>

<result>2</result>