1 4／5×25又5／8－20又5／12÷5＋5又1／6

1 4／5×25又5／8－20又5／12÷5＋5又1／6
=4/5*[25+5/8]-[20+5/12]*1/5+5+1/6
=4/5*25+4/5*5/8-20*1/5-5/12*1/5+5+1/6
=20+1/2-4-1/12+5+1/6
=21+7/12
=21又7/12
2 （5／3－7／5）÷（6－2／7）×4又2／7
=（5/3-7/5）*7/40*30/7
=[5/3-7/5]*3/4
=5/3*3/4-7/5*3/4
=5/4-21/20
=1/5
3 [6／5×（3／2－2／3）＋5又3／5]÷3又1／7
=[6/5*3/2-6/5*2/3+5+3/5]*7/22
=[9/5-4/5+5+3/5]*7/22
=[6+3/5]*7/22
=33/5*7/22
=21/10