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

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

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

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

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

\(\Leftrightarrow330y=-85920\)

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

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

\(\Rightarrow71+260=\frac{x-140}{x}+260\)

\(\Rightarrow71=\frac{x-140}{x}\)

\(\Rightarrow71x=x-140\)

\(\Rightarrow71x-x=-140\)

\(\Rightarrow70x=-140\)

\(\Rightarrow x=-2\)

\(b,\)\(y\times\frac{15}{2}-\frac{1}{3}\times\left(\frac{1}{4}+y\right)=90\frac{2}{3}\)

\(\Rightarrow\frac{15y}{2}-\frac{1}{12}-\frac{y}{3}=\frac{272}{3}\)

\(\Rightarrow\frac{90y}{12}-\frac{1}{12}-\frac{4y}{12}=\frac{1088}{12}\)

\(\Rightarrow90y-1-4y=1088\)

\(\Rightarrow86y=1089\)

\(\Rightarrow y=\frac{1089}{86}\)

a.1 là phân số nhé. Các bạn giúp mình với mình đang cần gấp

\(\frac{180\times123+9\times4567\times2+5310\times6}{\left(2+4+6+...+20+22\right)+48}\)

\(=\frac{18\times123+18\times4567+5310\times6}{132}\)

\(=\frac{116280}{132}=\frac{9690}{11}\)

mình bí rồi 

\(a.\left(x\times0,25+1999\right)\times2000=2052\times2000\\ \left(x\times0,25+1999\right)\times2000=4104000\\ x\times0,25+1999=4104000:2000\\ x\times0,25+1999=2052\\ x\times0,25=2052-1999\\ x\times0,25=53\\ x=53:0,25\\ x=212\)

hình như bn viết ngược 

                     bài giải

x + 140/x + 260=331

x nhân 2 + 140 =331-260=71

x nhân 2 =71 : 140 =0,50

      x= 0,50 : 2

      x=0,25

          hok tốt

\(71+65\) x 4 = \(\frac{x+140}{x+260}\)

=> 71 + 260 = \(\frac{x+140}{x+260}\)

=> \(331=\frac{x+140}{x+260}\)

=> \(331.\left(x+260\right)=x+140\)

=> \(331x+86060=x+140\)

=> \(331x-x=-86060+140\)

=>330x =- 85920

=> x = -2864/11

=> \(330x=-85920\)