Two cars A and B are driving towards each other at the same time from two places 367 kilometers apart. After 4.2 hours, the distance between the two cars is 28.9 kilometers. If A travels 0.5 kilometers more per hour than B, how many kilometers does B travel per hour?
甲乙两辆汽车从相距367千米的两地同时相向而行，4.2小时后两车还距28.9千米，如果甲每小时比乙多行0.5千米，乙每小时行多少千米？
<gadget id="calculator">367 - 28.9</gadget>
<output>338.1</output>

<gadget id="calculator">338.1 / 4.2</gadget>
<output>80.5</output>

<gadget id="calculator">80.5 - 0.5</gadget>
<output>80</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<result>40</result>