解：1/2-(1/4-1/6)=1/2-1/4+1/6=1/知段卜4+1/6=3/搭穗12+2/燃尘12=5/12
1/2－(1/缓橘4一没旦1/6)=2/4-1/4+1/6=1/扰察团4+1/6=3/12+2/12=5/12
1/2-(1/4-1/拆扮6)=6/12-(3/12-2/12)=6/激御余12-1/明滚12=5/12
