2, 3.( 1)-7 (2) 0 (3) 7/5 (4)-5/3 (5)-7 (6) 7

Three. 5.- 150+27=- 123

6 .a=4 b=2

7. Not necessarily (-2)+(-3) =-5-5

8. Not necessarily. Only a>0 and b> have | a+b | = | a |+b | at 0.

Otherwise, it may not be true, such as a = 3, b =- 1, | a+b | = 2, | a |+b | = 4.

After three or four. calculate

( 1) (+32)+(- 100/3)=-4/3

(2) (-5/6)+(- 1/6)=- 1

(3) 2.75+(- 1 1/4)=2.75-2.75=0

(4) 3.8+(-8.4)=-4.6