To build a road, 6.5km per day can be completed in 30 days. If you build 1.3km more every day, how many days can you finish the road ahead of time?
修一条公路，每天修6.5km，30天可以修完．如果每天多修1.3km，可以提前几天修完这条公路？
<gadget id="calculator">6.5 + 1.3</gadget>
<output>7.8</output>

<gadget id="calculator">30 / 7.8</gadget>
<output>3.846154</output>

<gadget id="calculator">6.5 * 3.846154</gadget>
<output>25.000001</output>

<gadget id="calculator">30 - 25.000001</gadget>
<output>4.999999</output>

<result>4.999999</result>