Lời giải:
Ta có: \(\frac{x+4}{7+y}=\frac{4}{7}\Leftrightarrow 7(x+4)=4(7+y)\)
\(\Leftrightarrow 7x=4y\)
\(\Leftrightarrow 11x=4y+4x=4(x+y)=4.22=88\)
\(\Leftrightarrow x=\frac{88}{11}=8\)
Suy ra \(y=22-x=22-8=14\)
Vậy \((x,y)=(8,14)\)
Từ \(\dfrac{x+4}{7+y}=\dfrac{4}{7}\) => ( x + 4) . 7 = (7 + y) . 4
=> 7x + 28 = 28 + 4y
=> 7x = 4y
=> \(\dfrac{x}{4}=\dfrac{y}{7}\) = \(\dfrac{x+y}{4+7}\) = \(\dfrac{22}{11}=2\) ( Áp dụng t/c dãy tỉ số bằng nhau)
=> \(\left\{{}\begin{matrix}\dfrac{x}{4}=2\\\dfrac{y}{7}=2\end{matrix}\right.\) => \(\left\{{}\begin{matrix}x=8\\y=14\end{matrix}\right.\)
Vậy x = 8 , y = 14
