1. 计算：
(1)$(-7.9)+4.3+2.9+(-1.3)$；
(2)$(-\dfrac{2}{3})+\dfrac{1}{2}+\dfrac{4}{5}+(-\dfrac{1}{2})+(-\dfrac{1}{3})$；
(3)$(-4\dfrac{2}{3})+(-3\dfrac{1}{3})+6\dfrac{1}{2}+(-2\dfrac{1}{4})$；
(4)$(-0.5)+3\dfrac{1}{4}+2.75+(-5\dfrac{1}{2})$；
(5)$(-1\dfrac{3}{5})+2\dfrac{1}{7}+(-2\dfrac{2}{5})+(-3\dfrac{1}{7})$；
(6)$1\dfrac{3}{4}+(-6.5)+3\dfrac{3}{8}+(-1.75)+2\dfrac{5}{8}$。

(1)原式$=-7.9+4.3+2.9-1.3=(-7.9+2.9)+(4.3-1.3)=-5+3=-2.$
(2)原式$=-\dfrac{2}{3}+\dfrac{1}{2}+\dfrac{4}{5}-\dfrac{1}{2}-\dfrac{1}{3}=-\dfrac{2}{3}-\dfrac{1}{3}+\dfrac{1}{2}-\dfrac{1}{2}+\dfrac{4}{5}=-1+\dfrac{4}{5}=-\dfrac{1}{5}.$
(3)原式$=-4\dfrac{2}{3}-3\dfrac{1}{3}+6\dfrac{1}{2}-2\dfrac{1}{4}=-8+4\dfrac{1}{4}=-3\dfrac{3}{4}.$
(4)原式$=[(-0.5)+(-5\dfrac{1}{2})]+(3\dfrac{1}{4}+2.75)=-6+6=0.$
(5)原式$=(-1\dfrac{3}{5}-2\dfrac{2}{5})+(2\dfrac{1}{7}-3\dfrac{1}{7})=-4+(-1)=-5.$
(6)原式$=1\dfrac{3}{4}+(-1.75)+3\dfrac{3}{8}+2\dfrac{5}{8}+(-6.5)=6+(-6.5)=-0.5.$

2. 计算：
(1)$(-5\dfrac{1}{4})-(+6\dfrac{13}{20})-(-1\dfrac{1}{4})$；
(2)$(-\dfrac{2}{3})-(-\dfrac{2}{3})-(+\dfrac{3}{4})$；
(3)$0.25+\dfrac{1}{12}+(-\dfrac{2}{3})-\dfrac{1}{4}+(-\dfrac{5}{12})$；
(4)$-(-1.08)-0.12-0.36$；
(5)$(-4\dfrac{1}{3})-[(-4\dfrac{1}{3})-(-3\dfrac{2}{3})]$；
(6)$\dfrac{5}{6}+(-2\dfrac{1}{2})-(-1\dfrac{1}{6})-(+0.5)$。

(1)原式$=-5\dfrac{1}{4}-6\dfrac{13}{20}+1\dfrac{1}{4}=-4-6\dfrac{13}{20}=-10\dfrac{13}{20}.$
(2)原式$=-\dfrac{2}{3}+\dfrac{2}{3}-\dfrac{3}{4}=-\dfrac{3}{4}.$
(3)原式$=(0.25-\dfrac{1}{4})+\dfrac{1}{12}+(-\dfrac{5}{12})+(-\dfrac{2}{3})=0+(-\dfrac{1}{3})+(-\dfrac{2}{3})=0+(-1)=-1.$
(4)原式$=1.08-0.12-0.36=0.6.$
(5)原式$=-4\dfrac{1}{3}+4\dfrac{1}{3}-3\dfrac{2}{3}=-3\dfrac{2}{3}.$
(6)原式$=\dfrac{5}{6}-2\dfrac{1}{2}+1\dfrac{1}{6}-\dfrac{1}{2}=\dfrac{5}{6}+1\dfrac{1}{6}-(2\dfrac{1}{2}+\dfrac{1}{2})=2-3=-1.$