To build a canal, it is planned to build 300 meters per day, and it will be completed in 8 days. In fact, it will be 400 meters per day, so how many days can it be completed in advance?
修一条水渠，计划每天修300米，8天修完，实际每天修400米，这样可以提前几天修完？
<gadget id="calculator">8 / 400</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">300 * (1/50)</gadget>
<output>6</output>

<gadget id="calculator">8 - 6</gadget>
<output>2</output>

<result>2</result>