:(-0.5)+(+3又4分之1)+(+6.75)+(-5又2分之1)

:(-0.5)+(+3又4分之1)+(+6.75)+(-5又2分之1)


(-0.5)+(+3又4分之1)+(+6.75)+(-5又2分之1)
= -(0.5+5又1/2)+(3又1/4+6.75)
= -6+10
=4