4/5-3/10+2/3=8/10-3/10+2/3 =5/10+2/3 =1/2+2/3 =3/6+4/6 =7/6.
4/5-3/10+2/3=8/10-3/10+2/3=5/10+2/3=1/2+2/3=3/6+4/6=7/6
一步一步算 7/6