(x-5)+(-31)=120

x-5=120-(-31)

x-5=120+31

x-5=151

x=151+5

x=156

1)

a) 2x + 5 = 3⁴ : 3²

2x + 5 = 3²

2x + 5 = 9

2x = 9 - 5

2x = 4

x = 4 : 2

x = 2

b) (3x - 24).73 = 2.74

(3x - 24).73 = 148

3x - 24 = 148/73

3x = 148/73 + 24

3x = 1900/73

x = 1900/73 : 3

x = 1900/219

c) [3.(42 - x)] + 15 = 23.3

126 - 3x + 15 = 69

141 - 3x = 69

3x = 141 - 69

3x = 72

x = 72 : 3

x = 24

d) 126 + (132 - x) = 300

132 - x = 300 - 126

132 - x = 174

x = 132 - 174

x = -42

2)

a) 120 - (x + 55) = 60

x + 55 = 120 - 60

x + 155 = 60

x = 60 - 55

x = 5

b) (7x - 11).3 = 25.52 + 200

(7x - 11).3 = 1500

7x - 11 = 1500 : 3

7x - 11 = 500

7x = 500 + 11

7x = 511

x = 511 : 7

x = 73

c) 2x + 2x + 4 = 544

4x = 544 - 4

4x = 540

x = 540 : 4

x = 135

3) 

a) 10 + 2x = 49 : 47

10 + 2x = 49/47

2x = 49/47 - 10

2x = -421/47

x = -421/47 : 2

x = -421/94

b) 70 - 5(x - 3) = 45

5(x - 3) = 70 - 45

5(x - 3) = 25

x - 3 = 25 : 5

x - 3 = 5

x = 5 + 3

x = 8

c) 4 + 95 : x = 143 : 142 - 23

4 + 95 : x = -3123/142

95 : x = -3123/142 - 4

95 : x = -3691/142

x = 95 : (-3691/142)

x = -13490/3691

\(\left(3x-25\right)-\left(x-9\right)=2-x\Leftrightarrow3x-25-x+9=2-x\Leftrightarrow2x-16-2+x=0\Leftrightarrow3x-18=0\)

\(\Leftrightarrow3x=18\Leftrightarrow x=6\)

\(2x+\left(-73-120\right)-\left(20-120\right)=5\Leftrightarrow2x-73-120-20+120=5\Leftrightarrow2x-93=5\)

\(\Leftrightarrow2x=98\Leftrightarrow x=49\)

๛๖ۣۜTɦủү❄๖ۣۜAɾĭαηηεツ Trình bày bài cho dễ nhìn nha -.-

\(\left(3x-25\right)-\left(x-9\right)=2-x\)

\(3x-25-x+9=2-x\)

\(\left(3x-x\right)-25+9=2-x\)

\(2x-16=2-x\)

\(2x+x=2+16\)

\(3x=18\)

\(x=6\)

\(2x+\left(-73-120\right)-\left(20-120\right)=5\)

\(2x+\left(-73\right)-120-20+120=5\)

\(2x+\left[\left(-73\right)-20\right]+\left(120-120\right)=5\)

\(2x+\left(-93\right)+0=5\)

\(2x+\left(-93\right)=5\)

\(2x=98\)

\(x=49\)

261

\(10,\Rightarrow x-14=-8\Rightarrow x=6\\ 11,\Rightarrow7-x-32=-25\\ \Rightarrow-25-x=-25\Rightarrow x=0\\ 12,\Rightarrow3x-16=\dfrac{2\cdot7^4}{7^3}=2\cdot7=14\\ \Rightarrow3x=30\Rightarrow x=10\\ 13,\Rightarrow\left[{}\begin{matrix}x-4=5\\x-4=-5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=9\\x=-1\end{matrix}\right.\\ 14,\Rightarrow\left(2x+11\right)^2=2^4:2^4=1\\ \Rightarrow\left[{}\begin{matrix}2x+11=1\\2x+11=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-5\\x=-6\end{matrix}\right.\\ 15,\Rightarrow7^{3x-2}=7^3\cdot4+7^3\cdot3=7^3\cdot7=7^4\\ \Rightarrow3x-2=4\\ \Rightarrow3x=6\Rightarrow x=2\)

10) x - [42 + (-28)] = -8

x - 14 = -8

x = -8 + 14 = 6

11) (7-x) - (25 +7) = -25

(7 -x) - 32 = -25

7 -x = -25 + 32 = 7

x = 7 -7 = 0

12) (3x - 2⁴) . 7³ = 2 . 7⁴

(3x - 16) . 343 = 4802

3x - 16 = 4802 : 343= 14

3x = 14 + 16 = 30

x = 30 : 3 =10

13) (x - 4)² = 25

⇒ 5² = 25

⇒ x - 4 = 5

⇒ x = 5 + 4 =9

14) 2⁴(2x + 11)² = 4²

16(2x + 11)² = 16

(2x + 11)² = 16 : 16 = 1

⇒ 2x + 11 = 1

⇒ 2x = 11 + 1 = 12

⇒ x = 12 : 2 = 6

15) 7^3x-2 - 3.7³ = 7³ . 4

7^3x-2 - 1029 = 1372

7^3x-2 = 1372 + 1029 = 2401

⇒ 7⁴ = 2401

⇒ 3x - 2 = 4

⇒ 3x = 4 + 2 = 6

⇒ x = 6 : 3 =2