Cars A and B are traveling towards each other from places A and B at the same time. Car A travels 80 kilometers per hour, and car B travels 70 kilometers per hour. The two cars meet at a distance of 20 kilometers from the midpoint. How long does it take for the two cars to meet? (Hint: How many kilometers did car A travel more than car B when they met)
甲、乙两车同时从A、B两地相向而行．甲车每个时行驶80千米，乙车每小时行驶70千米，两车在距离中点20千米处相遇，两车经过几小时相遇？(提示：相遇时，甲车比乙车多行了多少千米)
<gadget id="calculator">80 - 70</gadget>
<output>10</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 * (1/5)</gadget>
<output>4</output>

<result>4</result>