A machinery factory plans to produce 12 harvesters per day in April, and the task can be completed on time. If it produces 15 harvesters per day, how many days can the task be completed in advance?
某机械厂四月份计划每天生产12台收割机，可按时完成任务，如果每天生产15台，可提前几天完成任务？
<gadget id="calculator">30 / 15</gadget>
<output>2</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">30 - 24</gadget>
<output>6</output>

<result>6</result>