road has been built (2/5), and there are still 300 meters left. How many meters is this road?
修一条公路，已经修了(2/5)，还剩下300米，这条公路多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">300 / (3/5)</gadget>
<output>500</output>

<result>500</result>