3/4-3/4÷3+1/5 （8/7-4/5）*7/8 =3/4-1/4+1/5 = 1-7/10 =2/4+1/5 =3/10 =7/10 如果错了告诉我哈
3/4-3/4÷3+3/5=3/4-3/4×1/3+3/5=3/4-1/4+3/5=1/2+3/5=5/10+6/10=11/10（8/7-4/5）×7/8=8/7×7/8-4/5×7/8=1-7/10=3/10
