20% of the total length of a road has been repaired, and it is exactly 15 kilometers away from the midpoint. How many kilometers is the total length of this road?
一条路，已修了全长的20%，离中点正好还有15千米，这条路全长有多少千米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">15 / (3/10)</gadget>
<output>50</output>

<result>50</result>