1. 口算:
(1)$(-3)+(-9)=$
(3)$(-4)+6=$
(5)$6+(-6)=$
(7)$(-0.9)+1.5=$
(9)$(-10)+6=$
(11)$(-2.6)+(+1.2)=$
(13)$(-0.9)+(-2.7)=$
(15)$(-6.9)+2.3=$
(1)$(-3)+(-9)=$
-12
(2)$(-4.7)+3.9=$-0.8
(3)$(-4)+6=$
2
(4)$(-4)+4=$0
(5)$6+(-6)=$
0
(6)$0+(-6)=$-6
(7)$(-0.9)+1.5=$
0.6
(8)$\frac {1}{2}+(-\frac {2}{3})=$$-\frac{1}{6}$
(9)$(-10)+6=$
-4
(10)$(+12)+(-4)=$8
(11)$(-2.6)+(+1.2)=$
-1.4
(12)$(-3.2)+(+5.2)=$2
(13)$(-0.9)+(-2.7)=$
-3.6
(14)$\frac {2}{5}+(-\frac {3}{5})=$$-\frac{1}{5}$
(15)$(-6.9)+2.3=$
-4.6
(16)$(-1.5)+9=$7.5
答案：(1)-12 (2)-0.8 (3)2 (4)0 (5)0 (6)-6 (7)0.6 (8)$-\frac{1}{6}$ (9)-4 (10)8 (11)-1.4 (12)2 (13)-3.6 (14)$-\frac{1}{5}$ (15)-4.6 (16)7.5
2. 计算:
(1)$(-12)+\frac {1}{7};$ (2)$3.14+(-5.2);$ (3)$(-4.1)+(-15.61);$
(4)$(-9.2)+(-1\frac {3}{5});$ (5)$\frac {3}{10}+(-\frac {2}{5});$ (6)$(-1\frac {3}{4})+3\frac {1}{3}.$
(1)$(-12)+\frac {1}{7};$ (2)$3.14+(-5.2);$ (3)$(-4.1)+(-15.61);$
(4)$(-9.2)+(-1\frac {3}{5});$ (5)$\frac {3}{10}+(-\frac {2}{5});$ (6)$(-1\frac {3}{4})+3\frac {1}{3}.$
答案：(1)$-11\frac{6}{7}$ (2)-2.06 (3)-19.71 (4)$-10\frac{4}{5}$ (5)$-\frac{1}{10}$ (6)$\frac{19}{12}$
解析：
(1)$(-12)+\frac{1}{7}=-11\frac{6}{7}$
(2)$3.14+(-5.2)=-2.06$
(3)$(-4.1)+(-15.61)=-19.71$
(4)$(-9.2)+(-1\frac{3}{5})=-10\frac{4}{5}$
(5)$\frac{3}{10}+(-\frac{2}{5})=-\frac{1}{10}$
(6)$(-1\frac{3}{4})+3\frac{1}{3}=\frac{19}{12}$
(2)$3.14+(-5.2)=-2.06$
(3)$(-4.1)+(-15.61)=-19.71$
(4)$(-9.2)+(-1\frac{3}{5})=-10\frac{4}{5}$
(5)$\frac{3}{10}+(-\frac{2}{5})=-\frac{1}{10}$
(6)$(-1\frac{3}{4})+3\frac{1}{3}=\frac{19}{12}$