Respuesta :

Trancescient

(3) 8

Step-by-step explanation:

Note that ∆ADE is similar to ∆ABC. As such, the ratios of their legs are equal. Also note that AD = AB + BD.

BC/AB = DE/AD

BC/10 = 12/(10 + 5) = 12/15 = 4/5

or

BC = 10(4/5) = 8