(+2分之1)-(-5分之4)+(-3分之2)-(+2分之1)+(-3分之1)=

问题描述:

(+2分之1)-(-5分之4)+(-3分之2)-(+2分之1)+(-3分之1)=

=1/2+4/5-2/3-1/2-1/3
=(1/2-1/2)+4/5-(2/3+1/3)
=0+4/5-1
=-1/5