The road from A to B is 384 kilometers long. Two cars drive opposite each other. Car A travels 38 kilometers per hour, and car B travels 42 kilometers per hour. Car B starts after car A drives 64 kilometers first. How many hours after car B departs, the two cars meet?
A地到B地的公路长384千米，两辆汽车从两地相对开出，甲车每小时行38千米，乙车每小时行42千米．甲车先开出64千米后，乙车才出发．乙车出发后几小时两车相遇？
<gadget id="calculator">384 - 64</gadget>
<output>320</output>

<gadget id="calculator">38 + 42</gadget>
<output>80</output>

<gadget id="calculator">320 / 80</gadget>
<output>4</output>

<result>4</result>