Find the slope of the secant line on f joining the points at x = e and x = 2e.

Answer 1

The slope will depend upon the y values at x = e and x = 2e.

I have no idea what you mean by "the secant line on f"

You must have omitted a figure, or other parts of the question.

Answer 2

A secant line of a curve is a line that (locally) intersects two points on the curve.

You must know equation of curve f(x) if you want to find secant line.