a) \(\dfrac{25}{37}\times\dfrac{18}{29}+\dfrac{18}{29}\times\dfrac{12}{37}\)

\(=\dfrac{18}{29}\times\left(\dfrac{25}{37}+\dfrac{12}{37}\right)\)

\(=\dfrac{18}{29}\times\dfrac{37}{37}\)

\(=\dfrac{18}{29}\times1\)

\(=\dfrac{18}{29}\)

b) \(\dfrac{31}{85}\times\dfrac{11}{19}+\dfrac{31}{85}\times\dfrac{12}{19}-\dfrac{42}{19}\times\dfrac{31}{85}\)

\(=\dfrac{31}{85}\times\left(\dfrac{11}{19}+\dfrac{12}{19}-\dfrac{42}{19}\right)\)

\(=\dfrac{31}{85}\times\dfrac{-19}{19}\)

\(=\dfrac{31}{85}\times-1\)

\(=-\dfrac{31}{85}\)

c) \(\dfrac{16}{53}:\dfrac{17}{9}-\dfrac{16}{53}:\dfrac{17}{8}\)

\(=\dfrac{16}{53}:\left(\dfrac{9}{17}-\dfrac{8}{17}\right)\)

\(=\dfrac{16}{53}:\dfrac{1}{17}\)

\(=\dfrac{16}{901}\)

c) \(\dfrac{1}{5}\times\dfrac{12}{31}\times\dfrac{4}{3}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\dfrac{12}{31}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\left(\dfrac{12}{31}+\dfrac{19}{31}\right)\)

\(=\dfrac{4}{15}\times\dfrac{31}{31}\)

\(=\dfrac{4}{15}\times1\)

\(=\dfrac{4}{15}\)

a: =18/29*(25/37+12/37)

=18/29

b: =31/85(11/19+12/19-42/19)

=-31/85

c; =16/53(9/17+8/17)=16/53

d: =4/15(12/31+19/31)=4/15

a) -21 + (4 - x) = -17 + (-20) + 5

=>-21 + 4 - x = -32

=> -17 - x = -32

=> x = -17 + 32

=> x = 15

b) (15 - x) - (+9) = 34 - (-31)

=> 15 - x - 9 = 34 + 31

=> 6 - x = 65

=> x = 6 - 65

=> x = -59

c) (17 + x) - (-12) = -14 - (-10)

=> 17 + x + 12 = -14 + 10

=> 29 + x = -4

=>  x = -4 - 29

=> x = -33

c) (x + 24) + 15 = 8 - 17

=> x + 24  + 15 = -9

=> x + 39 = -9

=> x = -9 - 39

=> x = -48

A -21+ ( 4 - x ) = - 17 + ( -20 ) + 5

-21 + 4 - x = - 37 + 5

- 17 - x = - 32

-x = - 17 - ( - 32 )

-x = - 17 + 32

- x = 15

=> x = -15

B   ( 15 - x ) - ( + 9 ) = 34 - ( - 31 )

15 - x - 9 = 34 + 31

15 - 9 - x = 65

6 - x = 65

x = 6 - 65

x = -59

C , ( 17 + x ) - ( - 12 ) = - 14 - ( - 10 )

17 + x + 12 = - 14 + 10

29 + x = - 4

x = - 4 - 29

x = - 33

D , ( x + 24 ) + 15 = 8 - 17

x + 24 + 15 = - 9

x + 39 = -9

x = - 9 - 39

x = - 48

600 × x = 78 x 31 + 78 × 24 + 78 × 17 + 22 × 72

600 × x = 78 × (31 + 24 + 17) + 22 × 72

600 × x = 78 × 72 + 22 × 72

600 × x = 72 × (78 + 22)

600 × x = 72 × 100

600 × x = 7200

x = 7200 : 600

x = 12

Vậy x = 12

    2 x 17 + 38 x 17 + 31 x 17 + 29 x 17 

= 17 x ( 2 + 38 + 31 + 29 )

= 17 x 100

= 1700

2x17+38x17+31x17+29x17

=17x(2+38+31+29)

+17x100

=1700

2 x 17 + 38 x17 + 31 x 17 + 29 x 17

= 17 x ( 2 + 38 + 31 + 29 )

= 17 x 100

= 1700

Làm 1 câu thôi nhé lười lắm

1)

<=> 15 - x + 7 = -21

<=>     -x         = -21 - 15 - 7

<=>     -x         = -43

<=>      x         = 43

Các câu sau phá ngoặc đổi dấu, chuyển vế đổi dấu thôi kh có gì đâu

Bạn nhờ mình giúp cho

Câu cuối:

<=> -13 - 6 + x + 1 = 24

<=>               x        = 24 + 13 + 6 - 1

<=>               x        = 42

bạn lên mạng tra từng câu 1 sẽ có

ukm cảm ơn bạn nhìu

1/

$M=\frac{1}{3.8}+\frac{1}{8.13}+\frac{1}{13.18}+....+\frac{1}{33.38}$

$5M=\frac{8-3}{3.8}+\frac{13-8}{8.13}+\frac{18-13}{13.18}+...+\frac{38-33}{33.38}$

$=\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{18}+....+\frac{1}{33}-\frac{1}{38}$
$=\frac{1}{3}-\frac{1}{38}=\frac{35}{114}$

$\Rightarrow M=\frac{35}{114}:5=\frac{7}{114}$

2/

$N=\frac{1}{3.10}+\frac{1}{10.17}+\frac{1}{17.24}+\frac{1}{24.31}+\frac{1}{31.38}$

$7N=\frac{10-3}{3.10}+\frac{17-10}{10.17}+\frac{24-17}{17.24}+\frac{31-24}{24.31}+\frac{38-31}{31.38}$

$=\frac{1}{3}-\frac{1}{10}+\frac{1}{10}-\frac{1}{17}+\frac{1}{17}-\frac{1}{24}+\frac{1}{24}-\frac{1}{31}+\frac{1}{31}-\frac{1}{38}$

$=\frac{1}{3}-\frac{1}{38}=\frac{35}{114}$

$\Rightarrow N=\frac{35}{114}:7=\frac{5}{114}$

Bài 1. tìm x :

a, -16 + 23 + x = -16 

            23 + x = -16-(-16)

            23 + x = 0

                    x = 0 - 23 

            Vậy: x = -23

b, 2x - 35 = 15

    2x       = 15 + 35

    2x       = 50

      x       = 50 : 2

Vậy: x     = 25

c, 3x + 17 = 12

    3x        = 12 - 17

    3x        = -5 

Vậy: x        = -5/3

d, | x - 1 | = 0

      x - 1  = 0

      x       = 0 + 1

Vậy: x     = 1

e, -13 . | x | = -26

    -13 .  x   = -26

             x   = -26 : ( -13 )

     Vậy: x   = 2

Mik làm bài 1 còn bài 2 bn tự làm nha

Hok tốt!!!

=12/37 nha 

nhớ cho mình nha!