回复：回复：回复：how many left?

来源: 于 2010-01-13 18:23:15 [旧帖] [给我悄悄话] 本文已被阅读：次

I think you are smart enough to know how did I get 6. it is wrong:
(30-4x)+15-x=15. x=6 .there are 15 are on 6th mile.15-9=6.
intuition sometime is wrong.