f(x) = \frac{ln(x)}{x}

The gradient of the graph is given by f'(x) (Hint: use the quotient rule)

The gradient of the graph at x = e^2 is given by f'(e^2)

The y coordinate at the point where x = e^2 is given by f(e^2)

Now, you have the coordinates of a point and a gradient at that point. That is enough to find the equation of the tangent.

Post what you get! :)