factory processes a batch of parts. If it processes 200 parts per day, the task is completed 3 days earlier than the specified time. If it processes 120 parts per day, it takes 5 days longer to complete the task. How many days is the stipulated time to complete the task?
某工厂加工一批零件，如果每天加工200个，完成任务比规定时间提前3天，如果每天加工120个，完成任务比规时间多用5天，规定完成任务的时间是多少天？
<gadget id="calculator">120 * 5</gadget>
<output>600</output>

<gadget id="calculator">200 * 3</gadget>
<output>600</output>

<gadget id="calculator">600 + 600</gadget>
<output>1_200</output>

<gadget id="calculator">200 - 120</gadget>
<output>80</output>

<gadget id="calculator">1_200 / 80</gadget>
<output>15</output>

<result>15</result>