Xiaoqiang and Xiaodong set off from the same place in the same direction at the same time. Xiaoqiang walks 6 kilometers per hour, and Xiaodong rides a bicycle at 18 kilometers per hour. After 3 hours, how many kilometers are there between them?
小强和小东两人同时从同一地点向同一方向出发，小强步行每小时行6千米，小东骑自行车每小时行18千米，3小时候后，两人相距多少千米？
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">12 * 3</gadget>
<output>36</output>

<result>36</result>