(400-8)/(6+6*4/3)= 28 (秒)
甲的速度为 6*4/3 = 8 m/s,在相遇时甲乙共跑了400-8=392m,甲乙速度和为 6+8 = 14 m/s ,所以甲乙相遇需要 392/14 = 28 s