1. 口算:
(1)$(-3)-(-5)= $
2
; (2)$0-7= $
-7
;
(3)$|-1|-3= $
-2
; (4)$6-9= $
-3
;
(5)$(+4)-(-7)= $
11
; (6)$0-(-5)= $
5
;
(7)$-2.5-5.9= $
-8.4
; (8)$1.9-(-0.6)= $
2.5
;
(9)$2-8= $
-6
; (10)$-3-6= $
-9
;
(11)$(-8)-8= $
-16
; (12)$8-(-8)= $
16
;
(13)$8-8= $
0
; (14)$16-47= $
-31
;
(15)$28-(-14)= $
42
; (16)$(-3.8)-(+7)= $
-10.8
;
(17)$\left(-\dfrac{2}{5}\right)-\left(-\dfrac{3}{5}\right)= $
$\frac{1}{5}$
; (18)$\dfrac{1}{2}-\dfrac{1}{3}= $
$\frac{1}{6}$
;
(19)$\left(-\dfrac{1}{2}\right)-\dfrac{1}{3}= $
$-\frac{5}{6}$
; (20)$0-\left(-\dfrac{3}{4}\right)= $
$\frac{3}{4}$
;
(21)$(-2)-\left(+\dfrac{2}{3}\right)= $
$-2\frac{2}{3}$
; (22)$-\dfrac{1}{3}-\dfrac{1}{4}= $
$-\frac{7}{12}$
;
(23)$15.9-(-8.1)= $
24
; (24)$-17.3-(-5)= $
-12.3
.
答案：(1)2 (2)-7 (3)-2 (4)-3 (5)11 (6)5 (7)-8.4 (8)2.5 (9)-6 (10)-9 (11)-16 (12)16 (13)0 (14)-31 (15)42 (16)-10.8 (17)$\frac{1}{5}$ (18)$\frac{1}{6}$ (19)$-\frac{5}{6}$ (20)$\frac{3}{4}$ (21)$-2\frac{2}{3}$ (22)$-\frac{7}{12}$ (23)24 (24)-12.3
2. 计算:
(1)$-13-|-7|$; (2)$3\dfrac{1}{4}-0.75$; (3)$3\dfrac{7}{12}-\dfrac{3}{4}$;
(4)$10\dfrac{1}{3}-\dfrac{26}{5}$; (5)$\left(-\dfrac{1}{2}\right)-\left(-1\dfrac{1}{3}\right)$; (6)$\left(-2\dfrac{7}{10}\right)-\left(-3\dfrac{3}{5}\right)$.
答案：(1)-20 (2)$\frac{5}{2}$ (3)$\frac{17}{6}$ (4)$\frac{77}{15}$ (5)$\frac{5}{6}$ (6)$\frac{9}{10}$
解析：
(1)解：$-13-|-7|=-13-7=-20$
(2)解：$3\dfrac{1}{4}-0.75=\dfrac{13}{4}-\dfrac{3}{4}=\dfrac{10}{4}=\dfrac{5}{2}$
(3)解：$3\dfrac{7}{12}-\dfrac{3}{4}=\dfrac{43}{12}-\dfrac{9}{12}=\dfrac{34}{12}=\dfrac{17}{6}$
(4)解：$10\dfrac{1}{3}-\dfrac{26}{5}=\dfrac{31}{3}-\dfrac{26}{5}=\dfrac{155}{15}-\dfrac{78}{15}=\dfrac{77}{15}$
(5)解：$\left(-\dfrac{1}{2}\right)-\left(-1\dfrac{1}{3}\right)=-\dfrac{1}{2}+\dfrac{4}{3}=-\dfrac{3}{6}+\dfrac{8}{6}=\dfrac{5}{6}$
(6)解：$\left(-2\dfrac{7}{10}\right)-\left(-3\dfrac{3}{5}\right)=-\dfrac{27}{10}+\dfrac{18}{5}=-\dfrac{27}{10}+\dfrac{36}{10}=\dfrac{9}{10}$
