a)\(x.99+x=100\)

\(\Rightarrow x.\left(99+1\right)=100\)

\(\Rightarrow x.100=100\)

\(\Rightarrow x=1\)

b)\(420+65.x=\left(x+175\right):5+30\)

\(420+65.x=\left(x+175\right).\dfrac{1}{5}+30\)

\(420+65.x=\dfrac{1}{5}x+35+30=\dfrac{1}{5}x+65\)

\(\Rightarrow420-65=\dfrac{1}{5}x-65x\)

\(\Rightarrow-64,8x=355\)

\(\Rightarrow x=-\dfrac{1775}{324}\)

c)\(x:\left[\left(1800+600\right):30\right]=5600:\left(315-35\right)\)

\(x:80=20\Rightarrow x=20.80=1600\)

=10

=-67

=110

=110

=-110

=-192

a) 12 + ( 5 + x ) = 20 

⇔ 5 + x = 8

⇔ x = 3

Vậy x = 3

b) 120 + ( 50 + x ) = 180

⇔ 50 + x = 60

⇔ x = 10

Vậy x = 10

c) 175 + (  30 - x ) = 200

⇔ 30 - x = 25

⇔ x = 5

Vậy x = 5

d) 130 - ( 100 + x ) = 25

⇔ 100 + x = 105

⇔ x = 5

Vậy x = 5

e) 145 - ( 125 + x ) = 12

⇔ 125 + x = 133

⇔ x = 8

Vậy x = 8

j) 5 ( x + 12 ) + 22 = 92

⇔ 5x + 60 + 22 = 92

⇔ 5x + 82 = 92

⇔ 5x = 10

⇔ x = 2

Vậy x = 2

g) 3 ( x + 23 ) + 6 = 96

⇔ 3x + 69 + 6 = 96

⇔ 3x + 75 = 96

⇔ 3x = 21

⇔ x = 7

Vậy x = 7

Tìm x : 

a) 12 + ( 5 + x ) = 20

5 + x =20 - 12

5 +  x = 8

x = 3 

b) 120 + ( 50 + x ) = 180

50 + x = 180-120

50 + x = 60

x = 60 - 50

x = 10

c) 175 + ( 30 - x ) = 200

30 -x = 200 - 175

30 - x = 25

x = 30-25

x=5

d) 130- ( 100 +x ) =25

100 + x =130 - 25

100+x= 105

x=105-100

x=5

e) 145 - (125+x) = 12

125+x = 145-12

125+x=133

x= 133-125

x=8

j) 5 (x+12) +22 = 92 

5 ( x+12) = 92 -22

5 (x+12)=70

x+12=70 : 5

x + 12 = 14

x = 14-12

x=2

g) 2 (x+23) + 6 =96

2 (x+23) = 96 - 6

2 (x+23)= 90

x+23=90:2

x+23=45

x= 45-23

x=22

CHÚC BẠN HỌC TỐT

a) 12 + ( 5 + x ) = 20

=> 5 + x = 20 - 12

=> 5 + x = 8

=> x = 8 - 5

tìm x :

a) 12 + ( 5 + x ) = 20 

b) 120 + ( 50 + x ) = 180

c) 175 + (  30 - x ) = 200

d) 130 - ( 100 + x ) = 25

e) 145 - ( 125 + x ) = 12

j) 5 ( x + 12 ) + 22 = 92

g) 3 ( x + 23 ) + 6 = 96

giúp mk nha mn mk cần gấp

=> x = 3

b) 120 + ( 50 + x ) = 180

=> 50 + x = 180 - 120

=> 50 + x = 60

=> x = 60 - 50

=> x = 10

c) 175 + ( 30 - x ) = 200

=> 30 - x = 200 - 175

=> 30 - x = 25

=> x = 30 - 25

=> x = 5

d) 130 - ( 100 + x ) = 25

=> 100 + x  = 130 - 25

=> 100 + x = 105

=> x = 105 - 100 

=> x = 5

a

b

a) 30 + 192 + 70 = 30 + 70 + 192

= 100 + 192 = 292

b) 50 + 794 + 50 = 50 + 50 + 794

= 100 + 794 = 894

c) 75 + 219 + 25 = 75 + 25 + 219

= 100 + 219 = 319

d) 725 + 199 + 125 = 725 + 125 + 199

= 850 + 199 = 1 049

a) \(70-\left(x-3\right)=45\)

\(x-3=70-45\)

\(x-3=25\)

\(x=25+3\)

\(x=28\)

b) \(12+\left(5+x\right)=20\)

\(5+x=20-12\)

\(5+x=8\)

\(x=8-5\)

\(x=3\)

c) \(130-\left(100+x\right)=25\)

\(100+x=130-25\)

\(100+x=105\)

\(x=105-100\)

\(x=5\)

d) \(175+\left(30-x\right)=200\)

\(30-x=200-175\)

\(30-x=25\)

\(x=30-25\)

\(x=5\)

e) \(\left(x+12\right)+22=92\)

\(x+12=92-22\)

\(x+12=70\)

\(x=70-12\)

\(x=58\)

f) \(95-\left(x+2\right)=45\)

\(x+2=95-45\)

\(x+2=50\)

\(x=50-2\)

\(x=48\)

a)

70 - (x - 3) = 45

x - 3 = 70 - 45 = 25

x = 25 + 3 = 28

Vậy x = 28

b)

12 + (5 + x) = 20

5 + x = 20 - 12 = 8

x = 8 - 5 = 3

Vậy x = 3

c)

130 - (100 + x) = 25

100 + x = 130 - 25 = 115

x = 115 - 100 = 15

Vậy x = 15

d)

175 + (30 - x) = 200

30 - x = 200 - 175 = 25

x = 30 - 25 = 5

Vậy x = 5

e)

(x + 12) + 22 = 92

x + 12 = 92 - 22 = 70

x = 70 - 12 = 58

Vậy x = 58

f)

95 - (x + 2) = 45

x + 2 = 95 - 45 = 50

x = 50 - 2 = 48

Vậy x = 48

câu c sai r kìa bạn

14x + 54 = 82

14x = 28

x = 2

175 + (30 - x) = 2001

30 - x = 1826

x = 30 - 1826

x = - 1796

1551 - 10 ( x + 1 ) = 55

10(x + 1) = 1496

x + 1 = 149,6

x = 148,6

5 . (x + 12) + 22 = 92

5 . (x + 12) = 70

x + 12 = 14

x = 2

6 . (x + 23) + 40 = 100

6 . (x + 23) = 60

x + 23 = 10

x = - 13

\(14x+54=82\)

\(\Leftrightarrow14x=82-54\)

\(\Leftrightarrow14x=28\)

\(\Leftrightarrow x=2\)

Vậy \(x=2\)

\(175+\left(30-x\right)=2001\)

\(\Leftrightarrow30-x=2001-175\)

\(\Leftrightarrow30-x=1826\)

\(\Leftrightarrow x=-1796\)

Vậy \(x=-1796\)

\(1551-10\left(x+1\right)=55\)

\(\Leftrightarrow10.\left(x+1\right)=1551-55\)

\(\Leftrightarrow10.\left(x+1\right)=1496\)

\(\Leftrightarrow x+1=\frac{1496}{10}\)

\(\Leftrightarrow x=\frac{1486}{10}\)

Vậy \(x=\frac{1486}{10}\)

\(5.\left(x+12\right)+22=92\)

\(\Leftrightarrow5.\left(x+12\right)=70\)

\(\Leftrightarrow x+12=14\).

\(\Leftrightarrow x=2\)

Vậy \(x=2\)

\(6.\left(x+23\right)+40=100\)

\(\Leftrightarrow6.\left(x+23\right)=60\)

\(\Leftrightarrow x+23=10\)

\(\Leftrightarrow x=-13\)

Vậy \(x=-13\)

\(\left(x+175\right):x+30=548\)

\(\Rightarrow\left(x+175\right):x=518\)

\(\Rightarrow x+175=518x\)

\(\Rightarrow517x=175\)

\(\Rightarrow x=\frac{175}{517}\)

=>( X+175) : X= 548-30=518

=>X:X+175:X=518

=>1+175 : X=518

=>175 :X=517

=>X=175:517

=>X=175/517

  Vậy X=175/517