For a highway, the distance that has been repaired is unrepaired (2/5). If another 300 meters are repaired, half of the road will be repaired. What is the total length of this road in meters?
一条公路，已修的路程是未修的(2/5)，如果再修300米，就修好这条公路的一半．求这条公路的全长有多少米？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(7/2) - 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">300 / (3/2)</gadget>
<output>200</output>

<gadget id="calculator">200 * 2</gadget>
<output>400</output>

<result>400</result>