負數問題?

1.(＋5)＋(–7)
= 5–7
=-2

2. (–7)＋(–9)
=(–7)–9
=–12

3.(–7)–(–12)
= (–7)+12
= 5

4.(+5)–(–3)
= 5+3
= 8

5.(–3)x(+9)
= (–3)x9
= –27

6.(–7)x(–6)
= 7x6
=42

7.(–3)除(＋6)
= (–3)除6
= –0.5

8.(–5)除(–15)
= 5除15
= 0.3333333333333.........(無限個3)

9.(＋13)除(-39)
= 13除(-39)
= –0.33333333333.........(無限個3)

2007-09-02 15:54:17 補充：
比我做最佳回答,唔該!

2007-09-02 23:24:23 補充：
你好似抄我

１）(＋5)＋(–7)
=　+5-7
=　－２

２）(–7)＋(–9)

＝－７－９
＝－１６

３）(–7)–(–12)
＝－７＋１２
＝－１９

４）(＋5)–(–3)
＝＋５＋３
＝＋８

５）(–3)x(＋9)
＝－２７

６）(–7)x(–6)
＝＋４２

７）(–3)除(＋6)
＝－０．５

８）(–5)除(–15)
＝＋０．３３３３３．．．．．

９）(＋13)除(-39)
＝－０．３３３３３．．．．．

1. -2.
2. -16
3. +5
4. +8
5. -27
6. +42
7. -0.5
8. +0.3333..
9. -0.3333...

1)-2
2)-16
3)-19
4)+2
5)-27
6)-42
7)-5
8)-3
9)-30