Suppose $y$ varies inversely with $x$, and $y=5$ when $x=3$. What is the inverse variation equation that relates $x$ and $y$ ?

Step 1 ：We are given that $y$ varies inversely with $x$, and $y=5$ when $x=3$. The equation for inverse variation is $y = k/x$, where $k$ is the constant of variation.

Step 2 ：We can find the value of $k$ by substituting the given values of $x$ and $y$ into the equation. So, when $x = 3$ and $y = 5$, we get $k = 3*5 = 15$.

Step 3 ：The constant of variation, $k$, is 15. So, the inverse variation equation that relates $x$ and $y$ is $y = 15/x$.

Step 4 ：\(\boxed{y = \frac{15}{x}}\) is the final answer.