The engineering team built a road, originally planned to build 3.6 kilometers per day, and completed the repair in 20 days. The actual repair is 0.4 kilometers more than the plan every day. How many days before the actual repair?
工程队修一条公路，原计划每天修3.6千米，20天修完．实际每天比计划多修0.4千米，实际提前多少天修完？
<gadget id="calculator">3.6 + 0.4</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">3.6 * 5</gadget>
<output>18</output>

<gadget id="calculator">20 - 18</gadget>
<output>2</output>

<result>2</result>