A：B = 48:42 = 8:7速比脊乱同时根据速比=距离比：答：7/20 = 8/7 A = 8 / 20 A的跑开悔野斗碧磨 1-8/20 = 12/20 = 24 长度= 24 * 20/12 = 40
48X-42X=18*2 X=6 距离48X+42X=540km
