(-0.5)+(-2又三分之一)+2又四分之三+(-7/8)-(-1/2)的三次方
=-1/2 - 2-1/3 +2+3/4-7/8+1/8
=(-1/2-1/3)+(-2+2)+(3/4-7/8+1/8)
=-5/6+0+0
=-5/6