To build a railway, the full length (1/5) was repaired on the first day, and the rest (1/4) was repaired on the second day. At this time, there are still 12,000 meters left. How long is the total length of this railway in meters?
修一条铁路，第一天修了全长的(1/5)，第二天修了余下的(1/4)，这时还剩12000米，这条铁路全长多少米？
<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">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(4/5) * (1/4)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5) - (1/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">12_000 / (3/5)</gadget>
<output>20_000</output>

<result>20_000</result>