Pharaoh walked from home to the county town at 5 kilometers per hour, and rode his bicycle at 13 kilometers per hour when he returned home. The round trip took 3.6 hours. How many kilometers is the old Wang's house from the county seat?
老王步行从家去县城，每小时5千米，回家时骑车，每小时13千米，往返一共用了3.6小时．老王家距县城多少千米．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 13</gadget>
<output>1/13 = around 0.076923</output>

<gadget id="calculator">(1/5) + (1/13)</gadget>
<output>18/65 = around 0.276923</output>

<gadget id="calculator">3.6 / (18/65)</gadget>
<output>13</output>

<result>13</result>