and B ride bicycles from West Town to East Town at the same time. A travels 15 kilometers per hour, and B travels 10 kilometers per hour. After driving for 30 minutes, A returned to West Town at the original speed due to business, was delayed in West Town for 30 minutes, and then went to East Town at the same speed, and arrived 30 minutes later than B. Try to find the distance between the two towns.
甲、乙两人骑自行车同时从西镇出发去东镇，甲每小时行驶15千米，乙每小时行驶10千米．甲行驶30分钟后，因事用原速返回西镇，在西镇耽搁了30分钟，又以原速去东镇，结果比乙晚到30分钟，试求两镇间的距离．
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<result>10</result>