It takes 10 days for Team A to build a road alone, and 15 days for Team B to finish it alone. Teams A and B build it from both ends of the road at the same time, and the difference is 3 kilometers after 4 days. How many kilometers is this road?
修一条公路，甲队单独修完需要10天，乙队单独修完需要15天，甲乙两队从路的两端同时修，4天后还差3千米才修完．这条公路有多少千米？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) * 4</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3 / (1/3)</gadget>
<output>9</output>

<result>9</result>