A correspondent riding a bicycle needs to send letters to a certain place within the specified time. If he walks 15 kilometers per hour, he will be 0.4 hours early. If he walks 12 kilometers per hour, he will be 0.25 hours late. How far is his distance to a certain place? ?
一个通讯员骑自行车需要在规定时间内把信件送到某地，每小时走15千米可早到0.4小时，如果每小时走12千米就要迟到0.25小时，他去某地的路程有多远？
<gadget id="calculator">0.4 + 0.25</gadget>
<output>0.65</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

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

<gadget id="calculator">(1/12) - (1/15)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">0.65 / (1/60)</gadget>
<output>39</output>

<result>39</result>