Find DB.
We have similar triagles such that
BA / AC = BD / DE
( BD + DA) / AC = BD /DE
(BD + 7) / 12 = BD / 8 cross-multiply
8 (BD + 7) = 12 BD
8BD + 56 = 12BD
56 = 12BD - 8BD
56 = 4BD
BD = 56 / 4 = 14
