A road builder builds a road. The ratio of the length of the repaired to the unrepaired is 5:10. If another 390 meters are repaired, the ratio of the length of the repaired to the unrepaired is 2:3. How long is this road?
修路工人修一条路，已修和未修的长度比是5：10，如果再修390米，已修和未修的长度比是2：3，这条路有多长？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

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

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<gadget id="calculator">5 / 15</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) - (1/3)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">390 / (1/15)</gadget>
<output>5_850</output>

<result>5_850</result>