The engineering team plans to build a 400-kilometer road in 25 days, but actually builds 4 kilometers more than the original plan every day, so how many days can the task be completed in advance.
工程队计划25天修一条长400千米的公路，实际每天比原计划多修4千米，这样可以提前多少天完成任务．
<gadget id="calculator">400 / 25</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<gadget id="calculator">25 - 20</gadget>
<output>5</output>

<result>5</result>