ta có : \(7x=9y\Leftrightarrow x=\dfrac{9}{7}y\)
thay vào ta có : \(10x-8y=68\Leftrightarrow10.\dfrac{9}{7}y-8y=68\Leftrightarrow\dfrac{34}{7}y=68\)
\(\Leftrightarrow y=\dfrac{68}{\dfrac{34}{7}}=14\)
ta có : \(y=14\Rightarrow x=\dfrac{9}{7}y=\dfrac{9}{7}.14=18\) vậy \(y=14;x=18\)
7x=9y=>\(\dfrac{x}{9}=\dfrac{y}{7}\Rightarrow\dfrac{10x}{90}=\dfrac{8y}{56}=\dfrac{10x-8y}{90-56}=\dfrac{68}{34}=2\)
=>\(\left\{{}\begin{matrix}\dfrac{x}{9}=2\\\dfrac{y}{7}=2\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=18\\y=14\end{matrix}\right.\)
Vậy x=18,y=14
