a) 1-3+5-7+9-12+15-18

= (1+ 9) - (3+7) + (5+15) - (12+18) 

= 10 - 10 + 20 - 30 = -10.

b) (-2)+5-7+9-11+13-15+19-21

= 5 - 11 - 2 -2 = 5 - (11+2+2)

= 5 - 15 = -10 

Bài 1: 

a) Ta có: 1-3+5-7+9-12+15-18

=(1+9)-(3+7)+(5+15)-(12+18)

=10-10+20-30

=-10

b) Ta có: \(\left(-2\right)+5-7+9-11+13-15+19-21\)

\(=3+2+2+4-21\)

\(=5+6-21\)

=11-21=-10

Bài 2: 

a: =>x-35=-23

=>x=12

b: =>|x-8|=13

=>x-8=13 hoặc x-8=-13

=>x=21 hoặc x=-5

Bài 1: 

a: =42-98-42+12-12=-98

b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000

Bài 1: Thực hiện các phép tính sau:

\(a)\)Chưa rỏ đề

\(b)\)\(5025\div5-25\div5\)

\(=\)\(1005-5\)

\(=\)\(1000\)

\(c)\)\(218-180\div2\div9\)

\(=\)\(218-10\)

\(=\)\(208\)

\(d)\)\(\left(328-8\right)\div32\)

\(=\)\(320\div32\)

\(=\)\(10\)

Bài 1:

a) ( Tôi không nhìn rõ đầu bài )

b) 5025  :  5  -  25  :  5

=  ( 5025  -  25 )  :  5

=        5000   :   5

=       1000

c)   218  -  180  :  2  :  9

=     218   -    180  :  (  2  .  9 )

=      218    -    180   :  18

=       218    -    10

=       208

d)   (  328  -  8  )  :  32

=      320   :   32

=     10 

                                                                         Bài làm

1.

11 3/13 - ( 2 4/7 + 5 3/13 )

= 11 3/13 - 2 4/7 - 5 3/13

= ( 11 3/13 - 5 3/13 ) - 2 4/7

= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7

= ( 6 . 0 ) - 2 4/7

= 0 - 2 4/7

= 2 4/7

= 18/7

2 .

19 5/8 : 7/12 + ( -15 1/4) : 7/12

= { 19 5/8 + ( -15 1/4 ) } : 7/12

= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12

= { 4 . ( 5/8 + 2/8 ) } : 7/12

= ( 4 . 7/8 ) : 7/12

= 1.7/2 : 7/12

= 7/2 : 7/12

= 7/2 . 12/7

= 1.1/6.1

= 1/6

3 .

2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3

= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5

= 1/3 . 5/5 - 32/15 . 5/1

= 1/3 . 1 - 32.1/3.1

= 1/3 - 32/3

= -31/3

4 .

( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31

= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31

= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31

= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31

= 35/6 : 1/30 - 11/31

= 35/6 . 30/1 - 11/31

= 35.5/1.1 - 11/31

= 175 - 11/31

= 5425/31 - 11/31

= 5414/31

5.

75% - 1 1/5 + 0,5 : 5/12 - (-1/2)²

= 75/100 - 6/5 + 5/12 - 1/4

= 3/4 - 6/5 + 5/12 - 1/4

= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )

= 2/4 + ( 25/60 - 30/60 )

= 1/2 + (-5)/60

= 1/2 + (-1)/12

= 6/12 + (-1)/12

= 5/12

Đúng thì k cho mình nha !

1)

11 3/13 - ( 2 4/7 + 5 3/13 )

= 11 3/13 - 2 4/7 - 5 3/13

= ( 11 3/13 - 5 3/13 ) - 2 4/7

= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7

= ( 6 . 0 ) - 2 4/7

= 0 - 2 4/7

= 2 4/7

= 18/7

2 )

19 5/8 : 7/12 + ( -15 1/4) : 7/12

= { 19 5/8 + ( -15 1/4 ) } : 7/12

= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12

= { 4 . ( 5/8 + 2/8 ) } : 7/12

= ( 4 . 7/8 ) : 7/12

= 1.7/2 : 7/12

= 7/2 : 7/12

= 7/2 . 12/7

= 1.1/6.1

= 1/6

3 )

2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3

= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5

= 1/3 . 5/5 - 32/15 . 5/1

= 1/3 . 1 - 32.1/3.1

= 1/3 - 32/3

= -31/3

4 )

( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31

= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31

= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31

= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31

= 35/6 : 1/30 - 11/31

= 35/6 . 30/1 - 11/31

= 35.5/1.1 - 11/31

= 175 - 11/31

= 5425/31 - 11/31

= 5414/31

5)

75% - 1 1/5 + 0,5 : 5/12 - (-1/2)²

= 75/100 - 6/5 + 5/12 - 1/4

= 3/4 - 6/5 + 5/12 - 1/4

= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )

= 2/4 + ( 25/60 - 30/60 )

= 1/2 + (-5)/60

= 1/2 + (-1)/12

= 6/12 + (-1)/12

= 5/12

\(\left(1\right)\dfrac{-7}{12}.\dfrac{11}{8}-\dfrac{37}{8}.\dfrac{7}{12}+\dfrac{1}{2}=-\dfrac{7}{12}.\left(\dfrac{11}{8}+\dfrac{37}{8}\right)+\dfrac{1}{2}=-\dfrac{7}{12}.6+\dfrac{1}{2}=-3.\)

\(\left(2\right)\left(\dfrac{2}{3}-\dfrac{1}{4}-\dfrac{5}{6}\right).\left(-2\right)^2+\dfrac{3}{2}:\dfrac{-15}{4}=\dfrac{-5}{12}.4-\dfrac{2}{5}=\dfrac{-5}{3}-\dfrac{2}{5}=\dfrac{-31}{15}.\)

\(\left(3\right)\dfrac{-2}{5}+\dfrac{3}{10}-\dfrac{3}{5}+\dfrac{7}{10}-\dfrac{3}{2}=1-1-\dfrac{3}{2}=-\dfrac{3}{2}.\)

1. \(\dfrac{-7}{12}.\dfrac{11}{8}-\dfrac{37}{8}.\dfrac{7}{12}+\dfrac{1}{2}=\dfrac{-7}{12}\left(\dfrac{11}{8}+\dfrac{37}{8}\right)+\dfrac{1}{2}=\dfrac{-7}{12}.\dfrac{6}{1}+\dfrac{1}{2}=\dfrac{-7}{2}+\dfrac{1}{2}=\dfrac{-6}{2}=-3\)2.
\(\left(\dfrac{2}{3}-\dfrac{1}{4}-\dfrac{5}{6}\right).\left(-2\right)^2+\dfrac{3}{2}:\dfrac{-15}{4}=\dfrac{-5}{12}.4+\dfrac{-2}{5}=\dfrac{-5}{3}+\dfrac{-2}{5}=\dfrac{-31}{15}\)
3.
\(\dfrac{-2}{5}+\dfrac{3}{10}-\dfrac{3}{5}+\dfrac{7}{10}-\dfrac{3}{2}=\dfrac{-4}{10}+\dfrac{3}{10}-\dfrac{6}{10}+\dfrac{7}{10}-\dfrac{15}{10}=\dfrac{-15}{10}=\dfrac{-3}{2}\)

\(\dfrac{-7}{12}.\dfrac{11}{8}-\dfrac{37}{8}.\dfrac{7}{12}+\dfrac{1}{2}=\dfrac{-7}{12}.\left(\dfrac{11}{8}+\dfrac{37}{8}\right)+\dfrac{1}{2}=-\dfrac{7}{12}.6+\dfrac{1}{2}=-\dfrac{7}{2}+\dfrac{1}{2}=-3.\)

\(\left(\dfrac{2}{3}-\dfrac{1}{4}-\dfrac{5}{6}\right).\left(-2\right)^2+\dfrac{3}{2}:\dfrac{-15}{4}=\dfrac{8-3-10}{12}.4+\dfrac{-2}{5}=\dfrac{-5}{12}.4-\dfrac{2}{5}=\dfrac{-5}{3}-\dfrac{2}{5}=-\dfrac{31}{15}.\)

\(\dfrac{-2}{5}+\dfrac{3}{10}-\dfrac{3}{5}+\dfrac{7}{10}-\dfrac{3}{2}=\left(\dfrac{3}{10}+\dfrac{7}{10}\right)+\left(\dfrac{-2}{5}-\dfrac{3}{5}\right)-\dfrac{3}{2}=1-1-\dfrac{3}{2}=\dfrac{-3}{2}.\)

1: \(=\dfrac{7}{12}\left(-\dfrac{11}{8}+\dfrac{37}{8}\right)+\dfrac{1}{2}=\dfrac{7}{12}\cdot\dfrac{26}{8}+\dfrac{1}{2}=\dfrac{115}{48}\)

2: \(=\dfrac{8-3-10}{12}\cdot4+\dfrac{3}{2}\cdot\dfrac{-4}{15}\)

\(=\dfrac{-5}{3}+\dfrac{-12}{30}=\dfrac{-5}{3}+\dfrac{-2}{5}=\dfrac{-25-6}{15}=-\dfrac{31}{15}\)

3: \(=\dfrac{-2}{5}-\dfrac{3}{5}+\dfrac{3}{10}+\dfrac{7}{10}-\dfrac{3}{2}=-\dfrac{3}{2}\)

A.5/7

B.-481/391

C.0

D.-59/9

E.1

\(\dfrac{7}{-25}+\dfrac{18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)

=\(\left(\dfrac{-7}{25}+\dfrac{18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}\)

= \(\dfrac{11}{25} +1+\dfrac{5}{7}\)

= \(1\dfrac{11}{25}+\dfrac{5}{7}\)

= \(2\dfrac{27}{175}\)

b) \(-2+\dfrac{15}{19}+\dfrac{-15}{17}+\dfrac{15}{23}+\dfrac{4}{19}\)

=\(-2+\left(\dfrac{ }{ }\right)\)