原式=(-3又1/7)-(-6又2/5)-(+2又1/5)-(+5又6/7)
=(-3又1/7)+6又2/5+(-2又1/5)+(-5又6/7)
=[(-3又1/7)+(-5又6/7)]+(6又2/5-2又1/5)
=(-9)+4又1/5
= -(9-4又1/5)
= -4又4/5
原式=(-3又1/7)-(-6又2/5)-(+2又1/5)-(+5又6/7)
=(-3又1/7)+6又2/5+(-2又1/5)+(-5又6/7)
=[(-3又1/7)+(-5又6/7)]+(6又2/5-2又1/5)
=(-9)+4又1/5
= -(9-4又1/5)
= -4又4/5