天風有向數

5
(a) (-8)-(-5)=?
解：(-8)-(-5)
=(-8)+5
=-(8-5)
=-3
(b) (+9)+(-2)=?
解：(+9)+(-2)
=9-2
=7
(c) (+7)-(+12)=?
解：(+7)-(+12)
=7-12
=-(12-7)
=-5
(d) (-5)-(-6)=?
解：(-5)-(-6)
=(-5)+6
=6-5
=1
(e) (+5)+(-7)+(-10)=?
解：(+5)+(-7)+(-10)
=5-7-10
=-2-10
=-12
(f) (-6)-(-8)+(+5)=?
解：(-6)-(-8)+(+5)
=-6+8+5
=8-6+5
=2+5
=7
(g) (-3)+(-4)-(-7)=?
解：(-3(-4)-(-7)
=-3-4+7
=-7+7
=0
(h) (+4)-(-9)+(+5)=?
解：(+4)-(-9)+(+5)
=4+9+5
=13+5
=18