Given that points B, D, F are the midpoints of sides of triangle ΔACE.
Using Triangle's Mid-segment theorem, we can say that a line joining midpoints of two sides of a triangle is parallel and half of the length of the third side.
It means DF║AC and DF = [tex] \frac{AC}{2} [/tex]
Given DF = 15 in the question, so AC = 2·DF = 2×15 = 30.
So, AC = 30 is the final answer.
