To build a 350-meter-long tunnel, 150 meters were built in the first 3 days. According to this calculation, how many days will it take to complete the repair? (Solution with proportional knowledge)
修一条长350米的隧道，前3天修了150米，照这样计算，还要多少天才能修完？(用比例知识解)
<gadget id="calculator">350 - 150</gadget>
<output>200</output>

<gadget id="calculator">150 / 3</gadget>
<output>50</output>

<gadget id="calculator">200 / 50</gadget>
<output>4</output>

<result>4</result>