\(a,\Leftrightarrow x+9=39\Leftrightarrow x=30\\ b,\Leftrightarrow73-x=69\Leftrightarrow x=4\\ c,\Leftrightarrow x+7=38\Leftrightarrow x=31\\ d,\Leftrightarrow x+4=178\Leftrightarrow x=174\\ e,\Leftrightarrow2\left(x-51\right)=16+20=36\Leftrightarrow x-51=18\Leftrightarrow x=69\\ f,\Leftrightarrow x-19=9\Leftrightarrow x=28\\ g,\Leftrightarrow4\left(x-3\right)=49-1=48\Leftrightarrow x-3=12\Leftrightarrow x=15\)

a) 45 - ( x + 9 ) = 6

45 - x = 6 + 9

45 - x = 15

x = 45 - 15

x = 30

b) 89 - ( 73 - x ) = 20

89 - x = 20 + 73

89 - x = 93

x = 93 - 89

x = 4

c) 198 - ( x + 4 ) = 120

198 - x = 120 + 4

198 - x = 124

x = 198 - 124

x = 74

d) ( x + 7 ) - 25 = 13

x - 25 = 13 + 7

x - 25 = 20

x = 20 + 25

x = 45

e) 2 ( x - 51 ) = 2.2³ + 20

2 ( x - 51 ) = 64 + 20

2 ( x - 51 ) = 84

x - 51 = 84 - 2

x - 51 = 82

x = 82 + 51

x = 133

f) 450 : ( x - 19 ) = 50

450 : x = 50 - 19

450 : x = 41

x = 450 : 41

x = 24

a) \(58+7x=100\)

\(=>7x=100-58\)

\(=>7x=42\)

\(=>x=42:7\)

\(=>x=6\)

b) \(3x-7=28\)

\(=>3x=28+7\)

\(=>3x=35\)

\(=>x=35:3\)

\(=>x=\dfrac{35}{3}\)

c) \(x-56:4=16\)

\(=>x-14=16\)

\(=>x=16+14\)

\(=>x=30\)

d) \(101+\left(36-4x\right)=105\)

\(=>36-4x=105-101\)

\(=>36-4x=4\)

\(=>4x=36-4\)

\(=>4x=32\)

\(=>x=32:4\)

\(=>x=8\)

e) \(\left(x-12\right):12=12\)

\(=>x-12=12.12\)

\(=>x-12=144\)

\(=>x=144-12\)

\(=>x=132\)

f) \(\left(3x-2^4\right).7^3=2.7^4\)

\(=>3x-2^4=2.7^4:7^3\)

\(=>3x-16=2.7=14\)

\(=>3x=14+16\)

\(=>3x=30\)

\(=>x=30:3\)

\(=>x=10\)

i) \(\left(10+2x\right).4^{2011}=4^{2013}\)

\(=>10+2x=4^{2013}:4^{2011}\)

\(=>10+2x=4^2=16\)

\(=>2x=16-10\)

\(=>2x=6\)

\(=>x=6:2\)

\(=>x=3\)

\(#WendyDang\)

Ta có: \(2x+\frac76+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}+\frac{73}{72}+\frac{91}{90}=10\)

=>\(2x+1+\frac16+1+\frac{1}{12}+\ldots+1+\frac{1}{90}=10\)

=>\(2x+8+\left(\frac16+\frac{1}{12}+\cdots+\frac{1}{90}\right)=10\)

=>\(2x+8+\left(\frac12-\frac13+\frac13-\frac14+\cdots+\frac19-\frac{1}{10}\right)=10\)

=>\(2x+8+\left(\frac12-\frac{1}{10}\right)=10\)

=>\(2x+8+\frac{4}{10}=10\)

=>\(2x=10-8-\frac{4}{10}=2-\frac{4}{10}=2-\frac25=\frac85\)

=>\(x=\frac85:2=\frac45\)

c) \(\left|x\right|=3,5\Rightarrow\left[{}\begin{matrix}x=3,5\\x=-3,5\end{matrix}\right.\)

d) \(\left|x\right|=-2,7\Rightarrow x\in\varnothing\) 

l) \(\left|x+\dfrac{3}{4}\right|-5=-2\Rightarrow\left|x+\dfrac{3}{4}\right|=3\)

\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{3}{4}=3\\x+\dfrac{3}{4}=-3\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=3-\dfrac{3}{4}\\x=-3-\dfrac{3}{4}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{9}{4}\\x=\dfrac{15}{4}\end{matrix}\right.\)

Đính chính câu l \(x=-\dfrac{15}{4}\) không phải \(x=\dfrac{15}{4}\)

\(\frac{-21}{5}\)

x= -127/30 .

gợi ý các bạn chọn ( k) đúng cho mình 

a: =>7x=42

hay x=6

b: =>5x=35

hay x=7

c: =>x-14=16

hay x=30

d: =>36-4x=4

=>4x=32

hay x=8

e: =>x-12=144

hay x=156

f: =>3x-16=14

hay x=10

g: =>x+33=45

hay x=12

h: =>(x+9):2=39

=>x+9=78

hay x=69

a: =>7x=42

hay x=6

b: =>5x=35

hay x=7

c: =>x-14=16

hay x=30

d: =>36-4x=4

=>4x=32