Respuesta :

Secant-Secant Formula:
(whole secant) x (external part) =  (whole secant) x (external part)
In this case, AB*AC=AD*AE,
AB=AC-BC=12-6=6, so 6*12=4*AE => AE=18
DE=AE-AD=18-4=14
OE=half of DE=7