Bài 6:

\(21,251+6,058+0,749+1,042\)

\(=\left(21,251+0,749\right)+\left(6,058+1,042\right)\)

\(=22+7,1\)

\(=29,1\)

___________________

\(1,53+5,309+12,47+5,691\)

\(=\left(1,53+12,47\right)+\left(5,309+5,691\right)\)

\(=14+11\)

\(=25\)

5:

a: =>x/17=5/17

=>x=5

b; =>6+x=7/11*33=21

=>x=15

c: \(\dfrac{12+x}{43-x}=\dfrac{2}{3}\)

=>3x+36=86-2x

=>5x=50

=>x=10

d: \(\dfrac{x}{5}< \dfrac{3}{7}\)

=>x<3/7*5

=>x<15/7

f: 15/26+x/16=46/52

=>x/16=23/26-15/26=8/26=4/13

=>x=4/13*16=64/13

Tìm số nguyên x, biết:
1) -16 + 23 + x = - 16

7+x=-16

    x=-16-7

    x=-23
2) 2x – 35 = 15

2x=15+35

2x=50

  x=50:2

  x=25
3) 3x + 17 = 12

3x=12-17

3x=-5

  x=-5/3
4) (2x – 5) + 17 = 6

2x-5=6-17

2x-5=-11

2x=-11+5

2x=-6

  x=-6:2

  x=-3
5) 10 – 2(4 – 3x) = -4

2(4-3x)=10-(-4)

2(4-3x)=14

4-3x=14:2

4-3x=7

3x=4-7

3x=-3

  x=-3:3

  x=-1
6) - 12 + 3(-x + 7) = -18

3(-x+7)=-18-(-12)

3(x+7)=-6

x+7=-6:3

x+7=-2

    x=-2-7

    x=-9

tự đi mà làm

Bài 1:

a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)

b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)

c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)

d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)

hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)

e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)

hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)

dad

1, ( - 12 ) - ( 13 - x ) = - 15 - ( - 17 )

=> - 12  - 13 + x = - 15 + 17

=> - 25 + x = 2

=> x = 2 + 25 

=> x = 27 

2, 305 - x + 14 = 48 + ( x - 23 )

=> 305 - x + 14 = 48 + x - 23

=> x + x = 305 + 14 - 48 + 23

=> 2x = 294

=> x = 147

3, - ( x - 6 + 85 ) = ( x + 51 ) - 54

=> - x + 6 - 85 = x + 51 - 54

=> x + x = 6 - 85 - 51 + 54

=> 2x = - 76

=> x = - 38

4, - ( 35 - x ) - ( 37 - x ) = 33 - x

=> - 35 + x - 37 + x = 33 - x

=> x + x + x = 33 + 35 + 37

=> 3x = 105

=> x = 35

1.    x=-27

2.   x=147

3.   x=41

4    x=35 

Câu 1

(-12)-(3-x)=-15-(-17)

-12-3+x=-15+17

-15+x=2

x=17

Câu 2

305-x+14=48+(x-23)

319-x=25+x

2x=294

x=147

các câu còn lại giông nên mk ch đáp án

3,-38

4,35

a) 2x -18 = 10

    =>2x = 28

    => x = 14

b) 3x + 26 = 5

=> 3x = -21

=> x = -7

Ai làm cả 2 bài mình tích

3.|x+1|-2=4

3.|x+1|=4+2

3.|x+1|=6                                    

|x+1|=6:3

|x+1|=2

Trường hợp 1       x+1=2

x=2-1

x=1

trường hợp 2

x+1=-2

x=(-2)-1

x=-3

==> x thuộc {1; -3}

k mk nha chúc học tốt                                                                             

17 - 2x = -15

2x = 17 - (-15)

2x = 32

x = 32 : 2

x = 16

--------

54 : (x + 2) = -6

x + 2 = 54 : (-6)

x + 2 = -9

x = -9 - 2

x = -11

--------

12.(3 - x) = 72

3 - x = 72 : 12

3 - x = 6

x = 3 - 6

x = -3

-------

-3(x + 5) + 18 = -27

-3(x + 5) = -27 - 18

-3(x + 5) = -45

x + 5 = -45 : (-3)

x + 5 = 15

x = 15 - 5

x = 10

-------

(x + 5)² = 9

x + 5 = 3 hoặc x + 5 = -3

*) x + 5 = 3

x = 3 - 5

x = -2

*) x + 5 = -3

x = -3 - 5

x = -8

Vậy x = -8; x = -2

--------

(3 - x)³ = 27

(3 - x)³ = 3³

3 - x = 3

x = 3 - 3

x = 0

=00

- 3\(x\) + 24  = -24

  3\(x\)          = 24 + 24

   3\(x\)          = 48

     \(x\)           = 48 : 3

     \(x\)           = 16