b,Ta có:
\(x:5=y:2=\dfrac{x}{5}=\dfrac{y}{2};x-y=2\)
Áp dụng tcdtsbn , ta có:
\(\dfrac{x}{5}=\dfrac{y}{2}=\dfrac{x-y}{5-2}=\dfrac{30}{3}=10\)
\(\Rightarrow\left\{{}\begin{matrix}x=50\\y=20\end{matrix}\right.\)
d, Ta có:
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{2x}{2.2}=\dfrac{y}{5}=\dfrac{2x}{4}=\dfrac{y}{5}\)
Áp dụng tcdtsbn , ta có:
\(\dfrac{2x}{4}=\dfrac{y}{5}=\dfrac{2x-y}{4-5}=\dfrac{18}{-1}=-18\)
\(\Rightarrow\left\{{}\begin{matrix}x=-36\\y=-90\end{matrix}\right.\)