[tex]\it \dfrac{x}{y}=\dfrac{5}{9} \Rightarrow \dfrac{y}{x}=\dfrac{9}{5} \Rightarrow \dfrac{y}{x}=1,8 \Rightarrow y=1,8x\ \ \ \ \ \ (*)\\ \\ \\ \dfrac{5x-4y}{4x-5y}\ \stackrel{(*)}{=}\ \dfrac{5x-4\cdot1,8x}{4x-5\cdot1,8x}=\dfrac{5x-7,2x}{4x-9x}=\dfrac{-2,2x}{-5x}=\dfrac{2,2}{5}=0,44[/tex]
