（-2/配戚嫌培手3+(-1/6)-(-1/4)-(-1/2)
=-4/6-1/仔销6+1/4+2/4
=-5/6+3/4
=-10/12+9/12
=-1/12
负三分之二加负六分之一减负四分之一减负二分之一为什么等于负十二分之十九
（-2/配戚嫌培手3+(-1/6)-(-1/4)-(-1/2)
=-4/6-1/仔销6+1/4+2/4
=-5/6+3/4
=-10/12+9/12
=-1/12
（-2/配戚嫌培手3+(-1/6)-(-1/4)-(-1/2)
=-4/6-1/仔销6+1/4+2/4
=-5/6+3/4
=-10/12+9/12
=-1/12