There are two trains, train A is 200 meters long and travels 13 meters per second; train B is 150 meters long and travels 8 meters per second. Now two cars are traveling in the same direction on two parallel tracks, with A behind and B ahead. There is a tunnel in the middle of the road, the length of which is the same as that of car A. When the rear of car B has just left the tunnel, the front of car A has just entered the tunnel. How many seconds later, the fronts of the two cars are parallel.
有两列火车，甲车长200米，每秒行13米；乙车长150米，每秒行8米．现在两车在两条互相平行的轨道上同向而行，甲在后，乙在前．路当中有一条隧道，其长度和甲车长度相同．当乙车车尾刚离开隧道时，甲车车头刚进入隧道．则多少秒后，两车车头平行．
<gadget id="calculator">200 + 150</gadget>
<output>350</output>

<gadget id="calculator">13 - 8</gadget>
<output>5</output>

<gadget id="calculator">350 / 5</gadget>
<output>70</output>

<result>70</result>