(-3/4)×（-8+2/3-1/3）=(-3/4)×（1/3-8）=3/4×（8-1/3）=6-1/4=5又3/4
(-3/4)×（-8+2/3-1/3）=(-3/4)×(-8)+(-3/4)×2/3-(-3/4)×1/3=-6-1/2+1/4=-25/4
