A and B are walking toward each other from two places 36 kilometers apart. A's speed is 3 kilometers per hour, and B's speed is 4 kilometers per hour. If B starts for 2 hours before A, how many hours will A meet B?
甲乙二人从相距36千米的两地相向而行．甲速度为每小时3千米，乙速度为每小时4千米，若乙先出发2小时，甲才出发，则甲经过几小时后与乙相遇？
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">36 - 8</gadget>
<output>28</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">28 / 7</gadget>
<output>4</output>

<result>4</result>