\(\frac{5x-2y}{x+3y}=chong.copy.linhtinh\Leftrightarrow20\left(\frac{x}{y}\right)-8=7\left(\frac{x}{y}\right)+21\Rightarrow13\left(\frac{x}{y}\right)=29\)

 \(\Rightarrow copy.linhtinh=bieuthuc\)không hiểu nhận được qua tin nhắn (hiểu rồi thì càng tốt)

\(\frac{x}{y}=\frac{29}{13}\)

\(\frac{5-2x}{x+3y}=\frac{7}{4}\)

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\)

\(20x-8y=7x+21y\)

\(13x=29y\)

\(\frac{x}{y}=\frac{29}{13}\)

sao nhìn ảnh giống siêu trộm KID thế!

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\)

=> (5x - 2y).4 = 7.(x + 3y)

=> 20x - 8y = 7x + 21y

=>> 20x - 7x = 21y + 8y

=> 13x = 29y

\(\Rightarrow\frac{x}{y}=\frac{29}{13}\)

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\)

\(\Rightarrow4\left(5x-2y\right)=7\left(x+3y\right)\)

\(\Rightarrow20x-8y=7x+21y\)

\(\Rightarrow20x-7x=8y+21y\)

\(\Rightarrow13x=29y\)

\(\Rightarrow\frac{x}{y}=\frac{29}{13}\)

Vậy \(\frac{x}{y}=\frac{29}{13}\)

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\)

\(\Rightarrow7\left(x+3y\right)=4\left(5x-2y\right)\)

\(\Rightarrow7x+21y=20x-8y\)

\(\Rightarrow7x-20x=-8y-21y\)

\(\Rightarrow-13x=-29y\)

\(\Rightarrow13x=29y\)

\(\Rightarrow\frac{x}{y}=\frac{29}{13}\)

Vậy : \(\frac{x}{y}=\frac{29}{13}\)

Theo đế bài ta có:

\(20x-8y=7x+21y\)

\(\Leftrightarrow20x-7x=21y+8y\)

\(13x=21y\)

\(\Rightarrow\frac{x}{y}=\frac{21}{13}\)

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\)

\(\Rightarrow4\cdot\left(5x-2y\right)=7\cdot\left(x+3y\right)\)

20x - 8y = 7x + 21y

20x - 7x = 21y + 8y

13x = 29y

\(\Rightarrow\frac{x}{y}=\frac{29}{13}\)

\(\frac{5x-2y}{x+3y}=\frac{7}{4}\) => 4. (5x - 2y) = 7.(x+ 3y) => 20x - 8y = 7x + 21y

=> 20x - 7x = 8y + 21y => 13x = 29y => \(\frac{x}{y}=\frac{29}{13}\)

= 29/13

x - y = 7   =>  y = x - 7

Thay vào B ta có :

\(B=\frac{3-7}{2+\left(x-7\right)}-\frac{3.\left(x-7\right)+7}{2.\left(x-7\right)+x}=\frac{-4}{x-5}-\frac{3x-21+7}{2x-14+x}\)

     \(=\frac{-4}{x-5}-\frac{3x-14}{3x-14}=\frac{-4}{x-5}-1=\frac{-4}{x-5}-\frac{x-5}{x-5}=\frac{-4-\left(x-5\right)}{x-5}=\frac{1-x}{x-5}\)