A) => X = ( 357 - 7 ) : 5

=> X = 350 : 5

 => X = 70

B) 

=> ( x + 5 ) = ( 357 - 7 ) : 5

=> x + 5      = 350 : 5

=> x + 5      = 70

 =>      x       = 70 - 5

=>       x        = 65

357:[x+5]=5 dư 7

a: \(\left(\dfrac{1}{4}-x\right)\left(x+\dfrac{2}{5}\right)=0\)

=>\(\left[{}\begin{matrix}\dfrac{1}{4}-x=0\\x+\dfrac{2}{5}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{4}\\x=-\dfrac{2}{5}\end{matrix}\right.\)

b: \(\left|2x+1\right|+\dfrac{3}{2}=2\)

=>\(\left|2x+1\right|=\dfrac{1}{2}\)

=>\(\left[{}\begin{matrix}2x+1=\dfrac{1}{2}\\2x+1=-\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=-\dfrac{1}{2}\\2x=-\dfrac{3}{2}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=-\dfrac{1}{4}\\x=-\dfrac{3}{4}\end{matrix}\right.\)

c: (2x-3)²=36

=>\(\left[{}\begin{matrix}2x-3=6\\2x-3=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=9\\2x=-3\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=\dfrac{9}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)

d: \(7^{x+2}+2\cdot7^x=357\)

=>\(7^x\cdot49+7^x\cdot2=357\)

=>\(7^x=7\)

=>x=1

a) \(\left(\dfrac{1}{4}-x\right)\left(x+\dfrac{2}{5}\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\dfrac{1}{4}-x=0\\x+\dfrac{2}{5}=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{4}\\x=-\dfrac{2}{5}\end{matrix}\right.\)

\(---\)

b) \(\left|2x+1\right| +\dfrac{2}{3}=2\)

\( \Rightarrow\left|2x+1\right|=2-\dfrac{2}{3}\)

\(\Rightarrow\left|2x+1\right|=\dfrac{4}{3}\)

\(\Rightarrow\left[{}\begin{matrix}2x+1=\dfrac{4}{3}\\2x+1=-\dfrac{4}{3}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}2x=\dfrac{1}{3}\\2x=-\dfrac{7}{3}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{6}\\x=-\dfrac{7}{6}\end{matrix}\right.\)

\(---\)

c) \(\left(2x-3\right)^2=36\)

\(\Rightarrow\left(2x-3\right)^2=\left(\pm6\right)^2\)

\(\Rightarrow\left[{}\begin{matrix}2x-3=6\\2x-3=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}2x=9\\2x=-3\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{9}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)

\(---\)

d) \(7^{x+2}+2\cdot7^x=357\)

\(\Rightarrow7^x\cdot7^2+2\cdot7^x=357\)

\(\Rightarrow7^x\cdot\left(7^2+2\right)=357\)

\(\Rightarrow7^x\cdot\left(49+2\right)=357\)

\(\Rightarrow7^x\cdot51=357\)

\(\Rightarrow7^x=357:51\)

\(\Rightarrow7^x=7\)

\(\Rightarrow x=1\)

a, \(3x-357=156\)

\(\Rightarrow3x=513\)

\(\Rightarrow x=513:3\)

\(x=171\)

\(c,|x-3|=|-7|\)

\(TH1:x-3=7\Rightarrow x=10\)

\(TH2:x-3=-7\Rightarrow x=-4\)

KL:...

a,x-357=42369 

  x        = 42369  + 357

  x        =  42726

a) x-357=42369    

x = 42369 + 357 

x = 42726 

b) x:7=3214

x = 3214 x 7

x = 22498

a) x = 42726

b) x = 22498

\(357\div x=5\) dư 7

\(\left(357-7\right)\div x=5\)

\(350\div x=5\)

\(x=350\div5\)

\(x=70\)

x= (357-7):5= 350:5=70

357 : x = 5 dư 7

357 - 7 = x × 5

350 = x × 5

x = 350 : 5

x = 70

357 : (x + 5) = 5 (dư 7)

=> 350 : (x + 5) = 5

=> x + 5 = 350 : 5

=> x + 5 = 70

=> x = 70 - 5

=> x = 65

(357-7):(x+5)=5

350:(x+5)=5

x+5=350:5=70

x=70-5

x=65

=65

hok tốt

357 : X =5(dư 7)

        X  = ( 357 - 7 ) : 5

       X   = 350 : 5

       X   = 70

Vậy X = 70.

X : 23 =45(dư 6)

X        = 45 x 23 + 6

X        = 1041

Vậy X = 1041.

7 x (X-11)-6=757

7 x (X-11)   = 757 + 6

7 x (X-11)    = 763

      X - 11    = 763 : 7

      X - 11    = 109

     X            = 109 + 11

      X           = 120

Vậy X = 120.

Hok tốt !

x bawngf120 hok tốt 

nha