[102+(28-2x)]20=1*5

[102+(28-2x)]20=5

102+(28-2x)=5:20

102+(28-2x)=0.25

28-2x=0.25-102

28-2x=-101.75

2x=28+101.75

2x=129.75

x=129.75:2

x=64.875

123-5.(x+4)=38

 5(x+4)=123-38

 5(x+4)=85

 x+4=85:5

 x+4=17

 x=17-4

 x=13

10+2x=2.(3²-1)

 10+2x=2.(9-1)

 10+2x=2.8

 2x=16-10

2x=6

 x=6:2

 x=3

2.x-138=2³.3²

 2.x-138=72

 2.x=72+138

 2.x=210

 x=210:2

 x=105

[102+(28-2x)]:20-5=1

 (102+28-2x):20=6

 130-2x=120

 2x=130-120

 2x=10

 x=10:2

 x=5

231-(x-6)=1339:13

 231-(x-6)=103

 x-6=231-103

 x-6=128

 x=128+6

 x=134

123-5.(x+4)=38

5.(x+4)=123-38

5.(x+4)=85

(x+4)=85/5

x+4=17

x=17-4

x=13

10 + 2x = 2(3² - 1)

=> 10 + 2x = 2(9 - 1)

=> 10 + 2x = 2.8

=> 10 + 2x = 16

=> 2x = 16 - 10

=> 2x = 6

=> x = 6/2

=> x = 3

1.53x201=10653

2.

a)4 xX-15x4=6x15+X

<=>4x-60=90+x

<=>4x-x=60+90

<=>3x=150

<=>x=50

b(102+28-2x):20-5=1

<=>(130-2x):20=6

<=>130-2x=120

<=>2x=10

<=>x=5

c)1999x-x=1999+1997+1999

<=>1998x=5995

<=>\(x\approx3\)

d)105-5x=150:15

<=>105-5x=10

<=>5x=95

<=>x=19

e)(x+1)+(x+2)+(x+3)+...+(x+6)=78

<=>6x+21=78

<=>6x=57

<=>x=9,5

1) 53x201=53x200+53=10600+53=10653

2a)

4x-15x4=6x15+x

4x-60=90+x

4x-x=90+60

3x=150

x=50

b) x=5

c) x=3

d)x=19

e) x=9,5

các bạn ơi 4x và 3x là j vậy ??

c) 10 + 2x = 2(3² - 1)

10 + 2x = 16

2x = 6

x = 3

d) 2x - 138 = 2³.3²

2x - 138 = 72

2x = 72 + 138

2x = 210

x = 210/2 = 105

a) 1032 : (x : 4) = 6

x : 4 = 1032 : 6 = 172

X = 172 x 4 = 688

b) 123 - 5(x + 4) = 38

5(x +  4) = 123 - 38 = 85

x + 4 = 85/5 = 17

x = 17 - 4 = 13

f.x=134

g.x=5 ;x=-1 

h. x=388 ; x=-78

1 x 3 x 5 + 2 x 6  x 10 + 4 x 12 x 20

=15 + 120 + 960 

= 135 + 960 

=1095 

 1 x5 x 7 + 2 x 10 x 14 + 4 x 20 x 28

=35 + 280 + 2240 

= 2555

k nha 

????????????????????????????????????????????

1.3.5+2.6.10+4.12.20

=15+120+960

=135+960

=1095

a: \(=-25\cdot4-27=-100-27=-127\)

b: \(=-65:\left(-13\right)-25\cdot4=5-100=-95\)

c: \(=100\cdot\left(-47\right)+53\cdot\left(-100\right)=100\cdot\left(-100\right)=-10000\)

d: \(=\left[\left(-3\right)^{13}:3^{10}-73\right]:\left(-5\right)^2-14\)

\(=\left(-100\right):25-14=-4-14=-18\)

a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)

\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)

\(=\left(145\times100\right)-\left(143\times101\right)\)

\(=14500-14443\)

\(=57\)

b) \(54\times47-47\times53-20-27\)

\(=47\times\left(54-53\right)-20-27\)

\(=47-20-27\)

\(=0\)

c) \(10000-47\times72-47\times28\)

\(=10000-47\times\left(72+28\right)\)

\(=10000-47\times100\)

\(=10000-4700\)

\(=5300\)

d) \(3457-27\times48-48\times73+6543\)

\(=\left(3457+6543\right)-48\times\left(27+73\right)\)

\(=10000-48\times100\)

\(=10000-4800\)

\(=5200\)

a: =>x/27+1=-2/3

=>x/27=-5/3

=>x=-45

b: \(\Leftrightarrow x-4=\dfrac{2}{5}:\dfrac{20}{21}=\dfrac{2}{5}\cdot\dfrac{21}{20}=\dfrac{42}{100}=\dfrac{21}{50}\)

=>x=221/50

c: \(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{4}{60}=\dfrac{1}{15}\)

=>x=1/15-2/3=1/15-10/15=-9/15=-3/5

d: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{15}{14}\cdot\dfrac{21}{20}\)

=>\(x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{3}{2}\cdot\dfrac{3}{4}=\dfrac{1}{5}-\dfrac{9}{8}=\dfrac{-37}{40}\)

=>x=-37/24

e: =>-3/7x=84/45

=>x=-196/45

f: =>11/10x=-2/3

=>x=-20/33