26 + 5x = 3x - 56

5x - 3x = 56 - 26

5x - 3x = 30

2x = 30

  x = 30 : 2

  x = 15

26+5x=3x-56

=> 5x-3x=-56-26

=> 2x=-82

=> x=-82:2

=> x=-41

a) \(\overline{3x}+\overline{5x}-\overline{1x}=72\)

\(\Leftrightarrow\left(30+x\right)+\left(50+x\right)-\left(10+x\right)=72\)

\(\Leftrightarrow30+x+50+x-10-x=72\)

\(\Leftrightarrow x+70=72\)

\(\Leftrightarrow x=2\)

Vậy \(x=2\)

b) \(x.\left(x+1\right)=132\)

\(\Leftrightarrow x^2+x=132\)

\(\Leftrightarrow x^2+x-132=0\)

\(\Leftrightarrow x^2+12x-11x-132=0\)

\(\Leftrightarrow x.\left(x+12\right)-11.\left(x+12\right)=0\)

\(\Leftrightarrow\left(x-11\right).\left(x+12\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-11=0\\x+12=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=11\\x=-12\end{cases}}\)

Vậy \(x=11\)hoặc \(x=-12\)

mik nhầm nha, phải là:

138x=966

=> x=7

Ta có : 

\(\frac{3x-1}{40-5x}=\frac{25-3x}{5x-34}\)

\(=>\left(3x-1\right)\left(5x-34\right)=\left(40-5x\right)\left(25-3x\right)\)

\(=>15x^2-102x-5x+34=1000-120x-125x+15x^2\)

\(=>15x^2-107x+34=1000-245x+15x^2\)

\(=>34-107x=1000-245x\)

\(=>1000-245x+107x=34\)

\(=>1000-138x=34\)

\(=>138x=1000-34=966\)

\(=>x=\frac{966}{138}=7\)

Come on viết đề bài cho tử tế đi bạn (:

nhiều thế, ai lm nổi

Câu a:

\(\frac{x+5}{x+9}\) = \(\frac{x+4}{x+3}\)

(\(x\) + 5)(\(x+3\)) = (\(x+4\))(\(x+9\))

\(x^2\) + 3\(x\) + 5\(x\) + 15 = \(x^2\) + 9\(x\) + 4\(x\) + 36

\(x^2+3x+5x\) - \(x^2-9x\) - 4\(x\) = 36 - 15

(\(x^2-x^2\)) + (\(3x+5x\) - 9\(x-4x\)) = 21

0 + (8\(x\) - 9\(x\) - 4\(x\)) = 21

-\(x-4x\) = 21

-5\(x\) = 21

\(x\) = 21 : (-5)

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

Vậy \(x=-\frac{21}{5}\)