A road has already been repaired (2/5), and if it is repaired another 300 meters, half of the total length can be repaired. How many meters has the road been repaired?
一条公路已经修了它的(2/5)，再修300米，就能修好全长的一半．公路已经修了多少米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">300 / (1/10)</gadget>
<output>3_000</output>

<gadget id="calculator">3_000 * (2/5)</gadget>
<output>1_200</output>

<result>1_200</result>