To build a canal, the full length (1/5) was built on the first day, and the rest (1/4) was repaired on the second day, leaving 300 meters unrepaired. How many meters is the total length of this canal?
修一条水渠，第一天修了全长的(1/5)，第二天修了余下的(1/4)，还剩300米没有修，这条水渠总长有多少米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">300 / (3/4) / (4/5)</gadget>
<output>500</output>

<result>500</result>