Answer:
18
Step-by-step explanation:
Intersecting Secant-Tangent Theorem
The square of the tangent is equal to the product of the external secant segment and the secant.
Given:
- tangent = AE = 12
- external secant segment = EC = 8
- secant = ED = 18 + x
AE² = EC · ED
⇒ 12² = 8(18 + x)
⇒ 144 = 144 + 8x
⇒ 0 = 8x
⇒ x = 0
ED = 18 + x
= 18 + 0
= 18
