45% of the total length of a road has been built, and there is still 2,000 meters away from the midpoint. How long is this road in meters?
修一条公路，已经修了全长的45%，距离中点还有2000米，这条公路全长多少米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(1/2) - (9/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">2_000 / (1/20)</gadget>
<output>40_000</output>

<result>40_000</result>