∵原式 =0.75-19/7+0.125-89/7-33/8=0.75+0.125-19/7-89/7-33/8=0.875-108/7-33/8
=-18.68
∴0.75+(-2又5/7)-（-0.125)+(-12又 5/7)-4又1/8=18.68