(12)+(8)=

(12)+(8)=

12+(-3)-(+15)-(-4)
=12+(-3)+(-15)+4
=(12+4)+[(-3)+(-15)]
=16+(-18)
=-(18-16)
=-2

-5.27+3.8-1.2+(-0.5)-0.73
=(-5.27)+3.8+(-1.2)+(-0.5)+(-0.73)
=[(-5.27)+(-0.73)+(-1.2)+(-0.5)]+3.8
=(-7.7)+3.8
=-(7.7-3.8)
=-3.9

-4又7/8-5又1/2+(-4又1/2)-(+3又1/8)
=(-4又7/8)+(-5又1/2)+(-4又1/2)+(-3又1/8)
=[ (-4又7/8)+(-3又1/8) ] + [ (-5又1/2)+(-4又1/2) ]
=(-8)+(-10)
=-18

-3-5+7-9
=(-3)+(-5)+7+(-9)
=[(-3)+(-5)+(-9)] +7
=(-17)+7
=-(17-7)
=-10

1/3-1/2+1/4-1/6
=(1/3+1/4)-(1/2+1/6)
=7/12-8/12
=-(8/12-7/12)
=-1/12

(3-11)-(5-9)
=3-11-5+9
=(3+9)-(11+5)
=12-16
=-(16-12)
=-4

-|-1又1/3|-(+2/3)-|-3/5|+(-2/5)
=(-1又1/3)+(-2/3)+(-3/5)+(-2/5)
=-(1又1/3+2/3+3/5+2/5)
=-3追问?