Cars A and B set off from places A and B at the same time respectively, and drive back and forth at a constant speed during the rest of the day. If after two cars meet for the first time, car A continues to drive for 4 hours to reach B, while car B only travels for 1 hour to reach A, then the 15th time when the two cars meet (the number of encounters between A and B is not counted) , how many hours did they travel.
甲、乙两车分别从A、B两地同吋出发，且在人禱也住返来回勻速行驶．若两车笫一次相遇后，甲车继续行驶4小吋到达B，而乙车只行驶了1小吋就到达A，则两车笫15次(在A，B两地相遇次数不计)相遇吋，它们行驶了多少小吋．
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">6 * 14</gadget>
<output>84</output>

<gadget id="calculator">84 + 2</gadget>
<output>86</output>

<result>86</result>