@ @WS@ @ÖïÐaínÜaì@Þî†bjnÜa@ @ B DC A ABC [Aust.MC 1991] ( ) A>B >C 999 100 [Aust.MC 1991] ( ) 6 1000 4 [Aust.MC 1987] ( ) 12 [Aust.MC 1985] ( ) 1 ≤ x =/ y =/ z ≤ 30 z y x 3 () ASCENDENCE (AHSME 1993) ( ) 4×4