原式=(-7又2/7)-(-2又2/3)+4又3/7+4又1/3
=(-7又2/7)+2又2/3+4又3/7+4又1/3
=[(-7又2/7)+4又3/7]+(2又2/3+4又1/3)
=-(7又2/7-4又3/7)+7
=-2又6/7+7
=7-2又6/7
=4又1/7
原式=(-7又2/7)-(-2又2/3)+4又3/7+4又1/3
=(-7又2/7)+2又2/3+4又3/7+4又1/3
=[(-7又2/7)+4又3/7]+(2又2/3+4又1/3)
=-(7又2/7-4又3/7)+7
=-2又6/7+7
=7-2又6/7
=4又1/7