5/7*(7/5+2/3)
= 5/7*7/5+5/7*2/3
=1+10/21
=31/215分之4*99+5分之4简便计算4/5*99+4/5
=4/5*(99+1)
=4/5*100
=80
亲，一定要选为满意答案哦