答案
解:(1)(-2.8)-(+1.2),
=-2.8-1.2,
=-4;
(2)(-6)+(+5),
=-6+5,
=-1;
(3)-(-2)-|-3|,
=2-3,
=-1;
(4)(-
)-(-0.25),
=-
+0.25,
=0;
(5)(-0.6)+1.7+(+0.6 )+(-1.7 )+(-9 );
=(-0.6)+(+0.6)+1.7+(-1.7)+(-9),
=-9;
(6)|-2
|-(-2.5)+1-|1-2
|,
=2
+2.5+1-1
,
=6-1
,
=4
;
(7)3
-(-2
)+(-
)-
-(+
),
=3
+2
-
-
-
,
=3
-2-
,
=1.
解:(1)(-2.8)-(+1.2),
=-2.8-1.2,
=-4;
(2)(-6)+(+5),
=-6+5,
=-1;
(3)-(-2)-|-3|,
=2-3,
=-1;
(4)(-
)-(-0.25),
=-
+0.25,
=0;
(5)(-0.6)+1.7+(+0.6 )+(-1.7 )+(-9 );
=(-0.6)+(+0.6)+1.7+(-1.7)+(-9),
=-9;
(6)|-2
|-(-2.5)+1-|1-2
|,
=2
+2.5+1-1
,
=6-1
,
=4
;
(7)3
-(-2
)+(-
)-
-(+
),
=3
+2
-
-
-
,
=3
-2-
,
=1.