When building a road, when it reaches the full length (4/5), it is 15 kilometers away from the midpoint of the road. How many kilometers is the total length of the road?
修一条公路，当修到全长的(4/5)处时，距离这条公路中点15千米，这条公路全长多少千米？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

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

<result>50</result>