Answer: Line AC = 36
Step-by-step explanation: The first and most important clue is the fact that points B, D and F are midpoints of the triangle ACE. What this tells us is that point B divides line AC into two equal sides. Likewise points D and F. If point D divides line EC into two equal sides, then line ED equals
39/2 = 19.5
Also, triangle FED is similar to triangle AEC. Since ED is half of EC, and FE is half of AE. Therefore in triangles FED and AEC,
FD/ED = AC/EC
18/19.5 = AC/39
By cross multiplication we now have
(18 x 39)/19.5 = AC
702/19.5 = AC
36 = AC
Therefore line AC = 36
