共有28种方法!6-3+12+21=366-3+21+12=366+12-3+21=366+12+21-3=366+21-3+12=366+21+12-3=3612-3+6+21=3612-3+21+6=3612+6-3+21=3612+6+21-3=3612/6*(21-3)=3612+21-3+6=3612*(21-3*6)=3612*(21-3)/6=3612+21+6-3=361...