A road construction team builds a section of road, but what has been repaired is unrepaired (1/3). If another 10 kilometers are repaired, what has been repaired is unrepaired (2/5). How many kilometers is this section of road?
某修路队修一段公路，已修的是未修的(1/3)，如果再修10千米，已修的是未修的(2/5)，这段公路有多少千米？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/7) - (1/4)</gadget>
<output>1/28 = around 0.035714</output>

<gadget id="calculator">10 / (1/28)</gadget>
<output>280</output>

<result>280</result>