The distance between A and B is 54 kilometers. A and B are walking toward each other from the two places at the same time. A travels 4 kilometers per hour, and B travels 5 kilometers per hour. How many hours will they meet?
甲、乙两地相距54千米，A、B两人同时从两地相向而行，A每小时行4千米，B每小时行5千米，两人经过几小时后相遇？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">54 / 9</gadget>
<output>6</output>

<result>6</result>