<s>[INST] If $x:y = 7:3$ , then find the value of $\frac{y}{x-y}$ If $x:y = 7:3$ , then can I in order to find the value of $\frac{y}{x-y}$ replace $x$ and $y$ with $7$ and $3$ respectively ?
 [/INST] $ \frac{x-y}{y}=\frac{x}{y}-1=\frac{7}{3}-1=\frac{4}{3}$. Hence, what you want $=\frac{3}{4}$
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