有理数的加减法.1-4+3-0.5,-2.4+3.5-4.6+3.5,（-7）-（+5）+（-4)-(-10),

1-4+3-0.5
=(1+3)+[-4+(-0.5)]
=4+(-4.5)
=-(4.5-4)
=-0.5
-2.4+3.5-4.6+3.5
=[-2.4+(-4.6)]+(3.5+3.5)
=-7+7
=0
(-7)-(+5)+(-4)-(-10)
=(-7)+(-5)+(-4)+10
=-16+10
=-(16-10)
=-6
3/4-2/7+(-1/6)-(-2/3)
=3/4+(-2/7)+(-1/6)+2/3
=(3/4+2/3)+[-2/7+(-1/6)]
=17/12+(-19/42)
=17/12-19/42
=119/84-38/84
=27/28