To build a canal, 25% of the total length was repaired on the first day, and 30% of the total length was repaired on the second day, leaving 900 meters unrepaired. How long is this canal in meters?
修一条水渠，第一天修了全长的25%，第二天修了全长的30%，还剩下900米没修．这条水渠全长多少米？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (1/4) - (3/10)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">900 / (9/20)</gadget>
<output>2_000</output>

<result>2_000</result>