A highway is 18 kilometers long, and 4.5 kilometers were repaired in 3 days. According to this calculation, how many days will it take to complete the rest? (Solve with ratio)
一条公路全长18千米，3天修了4.5千米，照这样计算，剩下的还需要多少天才能修完？(用比例解)
<gadget id="calculator">18 - 4.5</gadget>
<output>13.5</output>

<gadget id="calculator">4.5 / 3</gadget>
<output>1.5</output>

<gadget id="calculator">13.5 / 1.5</gadget>
<output>9</output>

<result>9</result>