设快车速度为5xkm/h,慢车速度为4xm/h ,慢车开出时间是a小时,那么甲乙两地相距路程是
4x*a/(2/7)=14xa km,
则：(5x+4x)a+(1/5*14xa+11)=14xa
9xa+14xa/5+11=14xa
14xa/5+11=5xa
14xa+55=25xa
xa=5 km
14xa=5*14=70 km
即甲乙两地相距路程是70km .