Ta có: \(71+\left(65\times4\right)=\frac{y+140}{y+260}\)

\(\Leftrightarrow331=\frac{y+140}{y+260}\)

\(\Leftrightarrow331\left(y+260\right)=y+140\)

\(\Leftrightarrow331y+86060=y+140\)

\(\Leftrightarrow331y-y=140-86060\)

\(\Leftrightarrow330y=-85920\)

\(\Leftrightarrow y=\frac{-85920}{330}=\frac{-2864}{11}\)

\(\frac{x+140}{x}\)phân tích ra thành \(\frac{x}{x}+\frac{140}{x}\)đó Ngọc Nguyễn Minh 

x=2 đó LINH 

x=2 bạn nha

x=400x331

x=132400

tích nha!mk tích bn rùi đó

71+260=x/(140+260)

331=x/400

x=400x331=132400

331=x+140:x+260

331=x: [140+260]

331=x:400

x=331 nhân 400

x=132 400

   hok tốt

x = 2

* Cách giải lên lớp 6 học *

\(71+65\times4=\frac{x+140}{x}+260\)

\(\Leftrightarrow331=\frac{x+140}{x}+260\)

\(\Leftrightarrow71=\frac{x+140}{x}\)

\(\Leftrightarrow x+140=71.x\)

\(\Leftrightarrow140=71.x-x\)

\(\Leftrightarrow140=x\left(71-1\right)\)

\(\Leftrightarrow140=x70\)

\(\Leftrightarrow x=140:70=2\)