Since DC = 12, then EF also = 12.
Both AD and BC are indicated to be the same .
So AE = (24 - 12) / 2 = 12/2 = 6
Now you have a right triangle with height DE = 8 and base AE = 6
Using the Pythagorean Theorem we can now find AD:
AD = √(8^2 + 6^2)
AD = √(64 + 36)
AD =√100
AD = 10
