a) ( x - 15 ) - 75 = 0

      x - 15           = 75

      x                   = 75 + 15

      x                   = 90

Vậy x = 90

b) 575 - ( 6x + 70 ) = 445

                6x + 70   = 575 - 445

                6x + 70   = 130

                6x           = 60

                  x           = 10

Vậy x = 10

c) 315 + ( 125 - x ) = 435

                 125 - x  = 120

                          x  = 125 - 120

                          x  = 5

Vậy x = 5

d) x - 105 : 21 = 15

    x - 5            = 15

    x                 = 20

Vậy x = 20

e) ( x - 105 ) : 21 = 1

      x - 105           = 21

      x                     = 21 + 105

       x                    = 126

Vậy x = 126

a) (x-15)-75=0

x-15 = 0+75

x-15 = 75

x = 75 + 15

x = 90

b) 575-(6x+70)=445

6x+70 = 575-445

6x+70 = 130

6x = 130 - 70

6x = 60

x = 60:6

x = 10

d) x-105:21 = 15

x-105 = 15.21

x-105 = 315

x = 315 + 105

x = 420

e) (x-105):21 = 1

=> x-105 = 21

x = 105 + 21

x = 126

a ) ( x - 15 ) - 15 = 0  

        x - 15          = 15

        x                  = 15 + 15

        x = 30

a ) ( x - 15 ) - 15 = 0

       x - 15         = 0 + 15

       x - 15         = 15

câu d mk làm sai rồi

d) (x-15)-75=0

x-15=0+75=75

x=75+15=90

a, x= 15

b, x = 11

c, x =?

d, x = 90

e, ?

g, x=20

1)\(x-105:21=15\)

\(x-5=15\)

\(x=15+5\)

\(x=20\)

Vậy \(x=20.\)

2)\(\left(x-105\right):21=15\)

\(\left(x-105\right)=15.21\)

\(x-105=315\)

\(x=315+105\)

\(x=420\)

Vậy \(x=412.\)

4)\(1818:\left(6x-37\right)=18\)

\(6x-37=1818:18\)

\(6x-37=101\)

\(6x=101+37\)

\(6x=138\)

\(x=138:6\)

\(x=23\)

Vậy \(x=23.\)

mk quên,còn phần 3) nữa:

3)\(\left(32+x\right):17=x\)

\(32+x=x.17\)

\(\Leftrightarrow x=2\)

Vậy \(x=2.\)

a) \(315+\left(125-x\right)=435\)

\(\Leftrightarrow125-x=435-315\)

\(\Leftrightarrow125-x=120\)

\(\Leftrightarrow x=125-120\)

\(\Leftrightarrow x=5\)

b) \(x:41=32\)

\(\Leftrightarrow x=32\cdot41\)

\(\Leftrightarrow x=1312\)

c) \(\left(x-105\right):21=15\)

\(\Leftrightarrow x-105=15\cdot21\)

\(\Leftrightarrow x-105=315\)

\(\Leftrightarrow x=315+105\)

\(\Leftrightarrow x=420\)

d) \(x-105:21=15\)

\(\Leftrightarrow x-5=15\)

\(\Leftrightarrow x=15+5\)

\(\Leftrightarrow x=20\)

a, 315 + ( 125 - x ) = 435 

              ( 125 - x) = 435 - 315 

               ( 125 - x ) = 320

                          x   = 320 - 125 

                          x = 195

Bài 1: 

a: \(\dfrac{25}{42}-\dfrac{20}{63}=\dfrac{75-40}{126}=\dfrac{35}{126}=\dfrac{5}{18}\)

b: \(\dfrac{9}{20}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{135}{300}-\dfrac{52}{300}-\dfrac{50}{300}=\dfrac{33}{300}=\dfrac{11}{100}\)

a) 420 + 65 . 4 = ( x + 175 ) : 5 + 30

                 680 = ( x + 175 ) : 5 + 30

                           ( x + 175 ) : 5 = 680 - 30

                           ( x + 175 ) : 5 = 650

                             x + 175        = 650 . 5

                             x + 175        = 3250

                             x                   = 3250 - 175

                            x                    = 3075

Những câu sau làm giống vậy           

a.420 + 65 . 4 = ( x + 175 ) : 5 + 30

680 = ( x  + 175 ) : 5 + 30

( x  + 175 ) : 5  = 680 - 30

( x  + 175 ) : 5  = 650

  x  + 175 = 650 x 5

  x  + 175 = 3250

  x = 3250 - 175

  x = 3075

[ ( x + 32 ) - 17 ] . 2 = 42

[ ( x + 32 ) - 17 ]  =  42 : 2

 ( x + 32 ) - 17 = 21

 ( x + 32 ) = 21 + 17

 x + 32 = 38

x  = 38 - 32

x  =  6

b. ( 32 . 15 ) : 2 = ( x + 70) : 14 - 40

240 = ( x + 70 ) : 14 - 40

 ( x + 70 ) : 14 = 240 + 40

 ( x + 70 ) : 14 = 280

( x + 70 )  = 280 . 14

x + 70 = 3820

x = 3920 - 70

x  = 3850

a) => (x+32) - 17 = 42:2 = 21

=> x+32 = 21+17 = 38

=> x=38-32=6

b) => 61+(53-x) = 1785:17=105

=> 53-x = 105-61=44

=> x = 53-44 =9

c) => x^2 +54 -32 = 244:2 = 122

=> x^2 +22 = 122

=> x^2 = 122-2=100

=> x= 10 hoặc -10

giải oy pn **** giùm mk nka

a. X = 6

b. X = 9

c. X = 10

a)[(x+32)+17] :2=42

(x+32)+17=42.2

(x+32)+17=84

x+32=84-17

x+32=67

x=67-32

x=35

b)[61+(53-x)]:17=1785

61+(53-x)=1785.17

61+(53-x)=10345

53-x=30345-61

53-x=30284

x=53-30284

x=-30231