a, 1230 : 3(x – 20) = 10

3(x – 20) = 123

x – 20 = 41

x = 61

b, 250 – 10.(24 – 3x):15 = 244

10.(24 – 3x):15 = 6

10.(24 – 3x) = 90

24 – 3x = 9

3x = 15

x = 5

c,  4 x 3  + 15 = 47

4 x 3 = 32

x 3 = 8 = 2 3

x = 2

d,  65 - 4 x + 2 = 2014 0

65 - 4 x + 2 = 1

4 x + 2 = 64 = 4 3

x + 2 = 3

x = 1

e,  4 . 2 x - 3 = 125

4 . 2 x = 128

2 x = 32 = 2 5

x = 5

5-x-16=40+x

-x-x=40+16-5

(-x).2=51

-x=51/2=>x=51/2

1.x=40

2.x=10

3.x=

a) x+15 = 20-4x

=> x=1

b) 17-x=7-6x

=> x=-2

c) -12+x=5x-20

=> x=2

d) 4x-5=15-x

=> x=4

e) 9x-7=20-6x

=>x= \(\frac{9}{5}\)

g)2.(x-10)=3.(x-20)=x-4

=> x thuộc ∅

h) (x^2+2).(x-3) <0

=> x=3,...

a) -12+x=5x-20

-12+x  -5x = -20

-12+ ( -4x) = -20

-4x= -20-(-12)

-4x=-8

x= -8: (-4)

x= 2

Vậy....

Ko chắc nha

b) 4x-10=15-x

4x-10 +x=15

5x -10=15

5x= 15+10

5x= 25

x=25:5

x=5 

Vậy...

a, x+15=20-4x

=> x + 4x = 20 - 15

=> 5x = 5

=> x = 5 : 5

=> x = 1

b, 17-x=7-6x

=> -x + 6x = 7 - 17

=> 5x = - 10

=> x = -10 : 5

=> x = -2

c, 4.(x-5)-3.(x+7)= -19

=> 4x - 4.5 - 3.x + 3.7 = -19

=> 4x - 20 - 3x + 21 = -19

=> (4x-3x) + (21-20) = -19

=> 1x + 1 = -19

=> x = -19 - 1

=> x = -18

d, -7.(5-x)-2.(x-10)=15

=> -7x - (-7).5 - 2x - 2.10 = 15

=> -7x - (-35) - 2x - 20 = 15

=> -7x + 35 - 2x - 20 = 15

=> -7x+2x + (35-20) = 15

=> -5x + 15 = 15

=> -5x = 15 - 15

=> -5x = 0

=> x = 0 : (-5)

=> x = 0

e, -5.(2-x)+4.(x-3) = 10.x-15

=> -5x - (-5).2 + 4x - 4.3 = 10x - 15

=> -5x - (-10) + 4x - 12 = 10x - 15

=> -5x + 10 + 4x - 12 = 10x - 15

=> (-5x+4x) - (12-10) = 10x - 15

=> -1x - 2 = 10x - 15

=> -1x - 10x = -15 + 2

=> -11x = -13

=> x = \(\frac{-13}{-11}\)

a, 4x+18:2 = 13

4x+9 = 13

x = 1

b, 48 – 3(x+5) = 24

3(x+5) = 24

x + 5 = 8

x = 3

c,  2 x - 2 0 = 3 5 : 3 3

2x – 1 =  3 2

2x = 10

x = 5

d, (15+x):3 =  3 15 : 3 12

(15+x):3 =  3 3

(15+x):3 = 27

15 + x = 54

x = 39

a) \(-65-\left(x+15\right)+105=0\)

\(-65-\left(x+15\right)=-105\)

\(x+15=-65-\left(-105\right)\)

\(x+15=40\)

\(x=25\)

b) |-6| + (-9) - (x+1) = 7

-3- (x+1) =7

       x+1  = -10

       x      = -11

c)\(\left|5-x\right|+\left(-25+7\right)=-3-\left(-10\right)\)

    \(\left|5-x\right|+\left(-18\right)=7\)

    \(\left|5-x\right|=25\)

\(\Rightarrow\orbr{\begin{cases}5-x=25\\5-x=-25\end{cases}\Rightarrow\orbr{\begin{cases}x=-20\\x=30\end{cases}}}\)

d) \(28-\left|x+6\right|+\left(-2\right)=0\)

\(28-\left|x+6\right|=2\)

\(\left|x+6\right|=26\)

\(\Rightarrow\orbr{\begin{cases}x+6=26\\x+6=-26\end{cases}\Rightarrow\orbr{\begin{cases}x=20\\x=-32\end{cases}}}\)

e) \(x-\left(13-15\right)=5+\left(10-x\right)-\left(-1\right)\)

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

\(x+2=16-x\)

\(x+x=16-2\)

\(2x=14\)

\(x=7\)

f) \(-120-\left(x-5\right)=125\)

\(x-5=-120-125\)

\(x-5=-245\)

\(x=-240\)

g) \(10-\left(-5+2\right)+\left(-9\right)=\left(-20+7\right)-x\)

\(-16=-13-x\)

\(x=-13+16\)

\(x=3\)