六分之五除以百分之六十二点五
=(5/6)/(62.5%)
=(5/6)/(5/8)
=(5/6)*(8/5)
=4/3
八分之七除以四分之三加三分之四乘八分之一
=(7/8)*(4/3)+4/3*1/8
=(7/8+1/8)*(4/3)
=4/3
三分之七减（八分之五减八分之五除以十六分之十五）
=7/3-(5/8*-5/8*16/15)
=7/3-(5/8-2/3)
=7/3-5/8+2/3
=3-5/8
=2又3/8
83乘八十二分之八十一
=(82+1)*81/82
=81+1*81/82
=81又81/82