`[ ( 2 xx x - 11 ) : 3 + 1 ] xx 5 = 20`

`( 2 xx x - 11 ) : 3 + 1=20:5`

`( 2 xx x - 11 ) : 3 + 1=4`

`( 2 xx x - 11 ) : 3 =4-1`

`( 2 xx x - 11 ) : 3 =3`

`2xx x -11=3xx3`

`2xx x -11=9`

`2xx x =9+11`

`2 xx x=20`

`x=20:2`

`x=10`

Vậy `x=10`

`b,  x - 96 = ( 443 - x ) - 15`

`x-96=443-x-15`

` x+x=443-15+96`

`2x=524`

`x=524:2`

`x= 262`

Vậy `x=262`

\(#Nqoc\)

`a)`

\([ ( 2 \times x - 11 ) \div 3 + 1 ] \times 5 = 20\)

`(2 \times x - 11) \div 3 + 1 = 20 \div 5`

`(2 \times x - 11) \div 3 + 1 = 4`

`(2 \times x - 11) \div 3 = 4  - 1`

`(2 \times x - 11) \div 3 = 3`

`2 \times x - 11 = 3 \times 3`

`2 \times x - 11 = 9`

`2 \times x = 9 + 11`

`2 \times x = 20`

`x = 20 \div 2`

`x = 10`

Vậy, `x = 10`

`b)`

\(x - 96 = ( 443 - x ) - 15\)

`x - 96 = 443 - x - 15`

`x - 96 = 428 - x`

`x = 428 - x + 96`

`x = 524 - x`

`x - 524 + x = 0`

`(x + x) - 524 = 0`

`2x - 524 = 0`

`2x = 524`

`x = 524 \div 2`

`x = 262`

Vậy, `x = 262.` 

\(1,\Leftrightarrow x^2+10x+25=x^2-4x-21\\ \Leftrightarrow14x=-46\\ \Leftrightarrow x=-\dfrac{23}{7}\\ 2,\Leftrightarrow x^3+8=15+x^3+2x\\ \Leftrightarrow2x=-7\Leftrightarrow x=-\dfrac{7}{2}\\ 3,\Leftrightarrow\left(x+3\right)^2=0\\ \Leftrightarrow x=-3\\ 4,\Leftrightarrow x^3-9x^2+27x-27=0\\ \Leftrightarrow\left(x-3\right)^3=0\\ \Leftrightarrow x-3=0\Leftrightarrow x=3\\ 5,\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\\ \Leftrightarrow-12x=24\Leftrightarrow x=-2\\ 6,\Leftrightarrow x^2-3x+5x-15=0\\ \Leftrightarrow\left(x-3\right)\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)

e) 96-5(2x-1)=41

5(2x-1)= 96-41

5(2x-1)=55

2x-1=55:5

2x-1=11

2x=11+1

2x=12

x=12:2

x=6

a,    (x-12) -15 = (20-7) - (18+x)

<=> x - 12 - 15 = 13 - 18 - x 

<=> 2x = 22

<=> x = 11

b,     x- 96  = ( 443 - x) - 15

<=> x - 96 = 443 - x - 15

<=> 2x = 524

<=> x = 262

c,     311 - x + 82 = 46 + ( x- 21)

<=> 311 - x + 82 = 46 + x - 21

<=> 2x = 368

<=> x = 184

e,     ( - x + 821 + 534 ) = 499 + ( x-84)

<=> - x + 821 + 534 = 499 + x - 84

<=> 2x = 940

<=> x = 470

f,      x + 96 = ( 443 - x) - 447 

<=> x + 96 = 443 - x - 447

<=> 2x = - 100

<=> x = - 50

d,     - ( x - 3 + 85) = ( x + 70 - 71) -5

<=> - x + 3 - 85 = x + 70 - 71 - 5

<=> 2x = - 76

<=> x = - 38

a) x - 96 = (443 - x) - 15

x - 96 = 443 - x - 15

x + x = 443 -15 + 96

2x = 524

x = 524 : 2

x = 262

b) (x  -12) - 15 = (20 - 7) - (18 + x)

x - 12 - 15 = 20 - 7 - 18 - x

x + x = 20 - 7 - 18 + 12 + 15

2x = 22

x = 22 : 2

x = 11

c) 311 - x + 82 = 46 + (x - 21)

311 - x + 82 = 46 + x - 21

-x - x = 46 - 21 - 311 - 81

-2x = -367

x = -367 : (-2)

x = 183,5

d) -(x - 3 + 85) = (x + 70 - 71) - 5

-x + 3 - 85 = x + 70 - 71 - 5

-x - x = 70 - 71 - 5 - 3 + 85

-2x = 76

x = 76 : (-2)

x = -38

e,f làm tương tự

a) x - 96 = (443 - x) - 15

x - 96 = 443 - x - 15

x + x = 443 -15 + 96

2x = 524

x = 524 : 2

x = 262

b) (x  -12) - 15 = (20 - 7) - (18 + x)

x - 12 - 15 = 20 - 7 - 18 - x

x + x = 20 - 7 - 18 + 12 + 15

2x = 22

x = 22 : 2

x = 11

c) 311 - x + 82 = 46 + (x - 21)

311 - x + 82 = 46 + x - 21

-x - x = 46 - 21 - 311 - 81

-2x = -367

x = -367 : (-2)

x = 183,5

d) -(x - 3 + 85) = (x + 70 - 71) - 5

-x + 3 - 85 = x + 70 - 71 - 5

-x - x = 70 - 71 - 5 - 3 + 85

-2x = 76

x = 76 : (-2)

x = -38

e,f làm tương tự

a) x - 96 = (443 - x) - 15

x - 96 = 443 - x - 15

x + x = 443 -15 + 96

2x = 524

x = 524 : 2

x = 262

b) (x  -12) - 15 = (20 - 7) - (18 + x)

x - 12 - 15 = 20 - 7 - 18 - x

x + x = 20 - 7 - 18 + 12 + 15

2x = 22

x = 22 : 2

x = 11

c) 311 - x + 82 = 46 + (x - 21)

311 - x + 82 = 46 + x - 21

-x - x = 46 - 21 - 311 - 81

-2x = -367

x = -367 : (-2)

x = 183,5

d) -(x - 3 + 85) = (x + 70 - 71) - 5

-x + 3 - 85 = x + 70 - 71 - 5

-x - x = 70 - 71 - 5 - 3 + 85

-2x = 76

x = 76 : (-2)

x = -38

e,f làm tương tự

a, \(15:\left(x+2\right)=3\Leftrightarrow x+2=3\Leftrightarrow x=1\)

b, \(20:\left(x+1\right)=2\Leftrightarrow x+1=10\Leftrightarrow x=9\)

c, \(240:\left(x-5\right)=2^2.5^2-20=80\Leftrightarrow x-5=3\Leftrightarrow x=8\)

d, \(96-3\left(x+1\right)=42\Leftrightarrow3\left(x+1\right)=54\Leftrightarrow x+1=18\Leftrightarrow x=17\)

a) 15 : (x + 2) = 3

x + 2 = 15 : 3

x + 2 = 5

x = 5 – 2 = 3

b) 20 : (1 + x) = 2

1 + x = 20 : 2

1 + x = 10

x = 10 – 1 = 9

c) 240 : (x – 5) = 2².5² – 20

240 : (x – 5) = 4.25 – 20

240 : (x - 5) = 100 – 20

240 : (x - 5) = 80

x – 5 = 240 : 80

x – 5 = 3

x = 3 + 5 = 8

d) 96 - 3(x + 1) = 42

3(x + 1) = 96 – 42

3(x + 1) = 54

x + 1 = 54 : 3

x + 1 = 18

x = 18 – 1

x = 17

\(15\div\left(x+2\right)=3\)                                           \(20\div\left(1+x\right)=2\)

\(x+2=15\div3\)                                               \(1+x=20\div2\)

\(x+2=5\)                                                       1+x=10

x = 5 - 2                                                           x=9

x = 3

\(240\div\left(x-5\right)=2^2\cdot5^2-20\)                                \(96-3\left(x+1\right)=42\)

\(240\div\left(x-5\right)=80\)                                              \(3\left(x+1\right)=96-42\)

\(x-5=240\div80\)                                                 \(3\left(x+1\right)=54\)

x-5=3                                                                    \(x+1=54\div3\)

x=8                                                                        x+1=18

                                                                              x=17

Mng oi câu b 1202⁰ nha mng

Bài 1: 

a, 58.32 + 58.68 - 800

= 58.(32 + 68) - 800

= 58.100 - 800

= 5800 - 800

= 5000

b, 12020 + 280 : [55 - (7 - 4)³]

  =  12020 + 280 : [ 55 - 3³ ]

  =  12020 + 280 : [ 28]

  = 12020 + 10

  = 12030 

c, (96 - 19 - 45) - (55 + 96 - 119)

  = 96 - 19 - 45 - 55 - 96 + 119

 = (96 - 96) + (119 - 19) - (45 + 55)

= 0 + 100 - 100

= 0 

Bài 2:

a,7\(x\) - 70  = 105

   7\(x\)         = 105 + 70

   7\(x\)         = 175

     \(x\)          = 175 : 7

    \(x\)           = 25

\(\frac{x+3}{97}+\frac{x+5}{95}+\frac{x+4}{96}+\frac{x+1}{99}=-4\)

\(\left(\frac{x+3}{97}+1\right)+\left(\frac{x+5}{95}+1\right)+\left(\frac{x+4}{96}+1\right)+\left(\frac{x+1}{99}+1\right)=-4+4\)

\(\frac{x+100}{97}+\frac{x+100}{95}+\frac{x+100}{96}+\frac{x+100}{99}=0\)

\(\left(x+100\right).\left(\frac{1}{97}+\frac{1}{95}+\frac{1}{96}+\frac{1}{99}\right)=0\)

=> \(\orbr{\begin{cases}x+100=0\\\frac{1}{97}+\frac{1}{95}+\frac{1}{96}+\frac{1}{99}=0\end{cases}}\)

Mà \(\frac{1}{97}+\frac{1}{95}+\frac{1}{96}+\frac{1}{99}\ne0\)

=> x + 100 = 0

=> x = -100

Vậy x = -100

Câu b trừ mỗi số đi 1 tức là trừ cả cụm đó cho 3 rùi lm tương tự câu a

Tìm x:

x/1.2 + x/2.3+ x/3.4 +...+ x/2017.2018 = -1