Li Hua walked 4 kilometers per hour from the school to report to the winter camp 20.4 kilometers away. Half an hour later, the camp teacher heard the news and went to greet him. He walked 1.2 kilometers more per hour than Li Hua. Another 1.5 hours later, Zhang Ming rode his bike from school to the camp to report, but the three of them met somewhere on the way at the same time. How many kilometers does the cyclist travel per hour? (Write out the process of solving the problem)
李华以每小时步行4千米的速度从学较出发到20.4千米外的冬令营报到，半小时后，营地老师闻讯前往迎接，每小时比李华多走1.2千米．又过了1.5小时，张明从学校骑车去营地报到，结果三人同时在途中某地相遇．问骑车人每小时行驶多少千米？(写出解题过程)
<gadget id="calculator">4 * 0.5</gadget>
<output>2</output>

<gadget id="calculator">20.4 - 2</gadget>
<output>18.4</output>

<gadget id="calculator">4 + 1.2 + 4</gadget>
<output>9.2</output>

<gadget id="calculator">18.4 / 9.2</gadget>
<output>2</output>

<gadget id="calculator">2 + 0.5</gadget>
<output>2.5</output>

<gadget id="calculator">0.5 - 0.5 - 1.5</gadget>
<output>-1.5</output>

<gadget id="calculator">2 + (-1.5)</gadget>
<output>0.5</output>

<gadget id="calculator">4 / 0.5</gadget>
<output>8</output>

<gadget id="calculator">2.5 * 8</gadget>
<output>20</output>

<result>20</result>