(37 - x) / (x + 13) = 3 / 7

=> (37 - x) * 7 = (x + 13) * 3

=> 259 - 7x = 3x + 39

=> 7x - 3x = 259 -39

=> 4x = 220

=> x = 55

Vậy x = 55

 (37-x ) : ( x + 13 ) = 3/7 

=> 37-x = 3/7 . [x+13]

=> 37-x = 3/7 .x +39/7

=> 37 = 10/7 . x +39/7

=> 10/7 . x = 220/7 => x = 22

(37-x ) : ( x + 13 ) = 3/7 

=> 37-x = 3/7 . [x+13]

=> 37-x = 3/7 .x +39/7

=> 37 = 10/7 . x +39/7

=> 10/7 . x = 220/7 => x = 22

ko hiểu'

\(\dfrac{37-x}{x+13}=\dfrac{3}{7}\)

\(\Leftrightarrow7\left(37-x\right)=3\left(x+13\right)\)

\(\Leftrightarrow259-7x=3x+39\)

\(\Leftrightarrow259-39=3x+7x\)

\(\Leftrightarrow220=10x\)

\(\Leftrightarrow x=22\)

Vậy ..

\(=\frac{37-x}{x}=\frac{-88}{7}\)

\(-88x=7\left(37-x\right)\)

\(-88x=259-7x\)

\(-88x+7x=259\)

\(-81x=259\)

\(x=\frac{-259}{81}\)

\(\frac{37-x}{3}=\frac{x-13}{7}\)

\(\Rightarrow7\left(37-x\right)=3\left(x-13\right)\)

\(\Leftrightarrow259-7x=3x-39\)

\(\Leftrightarrow259+39=3x+7x\)

\(\Leftrightarrow298=10x\)

\(\Leftrightarrow x=29.8\)

\(\frac{37-x}{3}=\frac{x-13}{7}\)

\(\Rightarrow7\left(37-x\right)=3\left(x-13\right)\)

\(\Rightarrow259-7x=3x-39\)

\(\Rightarrow259+39=3x+7x\)

\(\Rightarrow298=10x\)

\(\Rightarrow x=\frac{298}{10}=\frac{149}{5}\)

       7(37-x) = 3(x-13)

<=> 259 - 7x = 3x -39

<=> 10x = 298

<=> x=\(\frac{298}{10}\)

<=> x = \(\frac{149}{5}\)

bạn viết lại đầu bài đi. Viết thế ai biết gì mà giải chứ