Two trains, A and B, start from two places 900 kilometers apart at the same time. A train travels 100 kilometers per hour. After 5 hours, it meets B. How many kilometers does B travel per hour?
甲、乙两辆火车从相距900千米的两地相向同时相对开出，甲车每小时行100千米，经过5小时候与乙车相遇，乙车每小时行多少千米？
<gadget id="calculator">900 / 5</gadget>
<output>180</output>

<gadget id="calculator">180 - 100</gadget>
<output>80</output>

<result>80</result>