-2.6+[-1.4+8又3/5-(3又2/3)]+4又2/3
=-2.6-1.4+8又3/5-3又2/3+4又2/3
=(-2.6-1.4)+8又3/5+(-3又2/3+4又2/3)
=-4+8又3/5+1
=5又3/5