A factory assembles TVs. If 20 sets are installed every day, the task can be completed in 15 days. In fact, 100 units were assembled in 4 days. According to this calculation, how many days can the task be completed? (Solved with proportional knowledge)
某厂装配电视机，如果每天装20台，15天可完成任务．实际4天就装配了100台，照这样计算，几天可以完成任务？(用比例知识解决)
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">300 / 25</gadget>
<output>12</output>

<result>12</result>