BE and CD are parallel, so the triangles ABE and ACD are similar. Then the following relation holds:
AE/AD = AB/AC
10/(10 + 8) = x/(x + 6)
Solve for x :
10 (x + 6) = x (10 + 8)
10x + 60 = 18x
8x = 60
x = 60/8 = 7/5
