A and B start from Dongzhen at the same time, and go to West Town, which is 20 kilometers apart, to do business. A rides a bicycle for 15 kilometers, and B walks 5 kilometers per hour. A went to Xizhen and finished his work in one hour, then returned along the original road. Encounter with B on the way. How far is the meeting place from Dongzhen?
甲，乙两同时从东镇出发，到相距20千米的西镇办事甲骑自行车时行15千米，乙步行每小时5千米．甲到西镇用一小时办完事情后沿原路返回．途中与乙相遇．问相遇处离东镇多远？
<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 * 2 * (1/4)</gadget>
<output>10</output>

<result>10</result>