a/ x - ( 25 - x) = x - 15

=> x - 25 + x = x - 15

=> 2x - x = -15 + 25

=> x = 10

b/ x - 8 = -13 - 8

=> x = -13 - 8 + 8 = -13

c/ x - (-15) = 5 - (-19)

=> x + 15 = 5 + 19 => x = 5 + 19 - 15 = 9

d/ (x + 35) = 2x + 15 + (13 - 4)

=> x + 35 = 2x + 15 + 13 - 4

=> x - 2x = 15 + 13 - 4 - 35

=> -x = -11 => x = 11

e/ 5 - 2x = 15-(-9) - 3x

=> 5 - 2x = 15 + 9 - 3x

=> -2x + 3x = 15 + 9 - 5

=> x = 19

g/ x + 135 = 3x - 15

=> x - 3x = -15 - 135

=> -2x = -150

=> x = -150/ - 2 = 75

câu 1:

a) 500-(300)-190+(-210)

= 500-300-190-210

= 200 - 210 -190

=-10 - 190

=-200

b) (-3)³ .5+12.(-6)

= -27.5 -72

=-135 - 72

=-207

c) 15.(-19-4)-19.(15-4)

= 15.(-23) - 19.11

=-345 - 209

=-554

câu 2: tìm x thuộc Z

a) 3x-2=3

=> 3x=3/2

=> x=1/2

b) x chia hết cho 5 và -7<x<11

=> x thuộc {-5;0;5;10}

Câu 1: 

a) Ta có: \(500-\left(300\right)-190+\left(-210\right)\)

\(=500-300-190-210\)

\(=\left(500-300\right)-\left(190+210\right)\)

\(=200-400=-200\)

b) Ta có: \(\left(-3\right)^3\cdot5+12\cdot\left(-6\right)\)

\(=\left(-3\right)^3\cdot5-3\cdot4\cdot3\cdot2\)

\(=-5\cdot3^3-3^2\cdot8\)

\(=3^2\cdot\left(-5\cdot3-8\right)\)

\(=9\cdot\left(-15-8\right)=9\cdot\left(-23\right)=-207\)

c) Ta có: \(15\cdot\left(-19-4\right)-19\cdot\left(15-4\right)\)

\(=-15\cdot19-15\cdot4-15\cdot19+19\cdot4\)

\(=-30\cdot19+4\cdot4\)

\(=-2\cdot\left(15\cdot19+2\cdot4\right)\)

\(=-2\cdot\left(285+8\right)=-586\)

Giải lần lượt từng bất phương trình:

-2x+15 < 3x- 7 <=> 5x > 22 <=> x > 4,4

3x-7 < 19-x <=> 4x < 26 <=> x < 6,5

Kết hợp 2 bất phương trình ta đc 4,4 <x <6,5

Vậy x=5 hoặc x=6

Chúc bạn học tốt!

a) \(12+x+\left(-5\right)=-18-2x\)

\(\Rightarrow12+x-5=-18-2x\)

\(\Rightarrow x+7+18+2x=0\)

\(\Rightarrow3x=-25\)

\(\Rightarrow x=-\dfrac{25}{3}\) 

b) \(\left(-14\right)-x+\left(-15\right)=-10+\left(4-2x\right)\)

\(\Rightarrow-14-x-15=-10+4-2x\)

\(\Rightarrow-x-29=-2x-6\)

\(\Rightarrow-x+2x=-6+29\)

\(\Rightarrow x=23\)

c) \(x-\left(-19\right)-\left(-11\right)=-\left(3x+40\right)\)

\(\Rightarrow x+19+11=-3x-40\)

\(\Rightarrow x+30=-3x-40\)

\(\Rightarrow x+3x=-40-30\)

\(\Rightarrow4x=-70\)

\(\Rightarrow x=-\dfrac{35}{2}\)

a) 42 - x = 5

x = 42 - 5

x = 37

b) 15.(x + 4) = 75

x + 4 = 75 : 15

x + 4 = 5

x = 5 - 4

x = 1

d) x + 18 = 12

x = 12 - 18

x = -6

e) 2x - 15 = -19

2x = (-19) + 15

2x = -4

x = -4 : 2

x = -2

f) 36 : (x^3 - 12) = -3

x^3 - 12 = 36 : (-3)

x^3 - 12 = -12

x^3 = 0

=> x = 0

g)x + 15 = 35

x = 35 - 15

x = 20

h) 2x - 13 = 3^2

2x - 13 = 9

2x = 9 + 13

2x = 22

x = 22 : 2

x = 11

a) 42-x=5

         x=42-5

         x= 37

b)15*(x+4)=75

        x+4=75:15

        x+4=5

        x    =5-4

       x     = 1

a) 42 - x = 5

x = 42 - 5

x = 37

b) 15.(x + 4) = 75

x + 4 = 75 : 15

x + 4 = 5

x = 5 - 4

x = 1

d) x + 18 = 12

x = 12 - 18

x = -6

e) 2x - 15 = -19

2x = (-19) + 15

2x = -4

x = -4 : 2

x = -2

f) 36 : (x^3 - 12) = -3

x^3 - 12 = 36 : (-3)

x^3 - 12 = -12

x^3 = 0

=> x = 0

g)x + 15 = 35

x = 35 - 15

x = 20

h) 2x - 13 = 3^2

2x - 13 = 9

2x = 9 + 13

2x = 22

x = 22 : 2

x = 11