L.K. 發表於 6-9-2008 22:09:06

問

the prime minister A,B,C,D,E,F,G of 7 countries will address at a summit meeting.
find the nuber of arrangenment that can be made so that A will speak before C

[ 本帖最後由 L.K. 於 7-9-2008 00:18 編輯 ]
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