Answer:
AD = 4.5
Explanation:
Since the two bases of the two given triangles are parallel the triangles are similar.
Triangle BDE is similar to Triangle BAC
From this the following proportion can be set up.
BE / BC = BD/BA
BE = 8
BC = 8+12 = 20
BD = 3
BA = 3 + x where x = DA
8/20 = 3/(3+x) Cross Multiply
8(3 + x) = 3 * 20 Remove the brackets on the left. Combine Right
24 + 8x = 60 Subtract 24 from both sides
8x = 60 - 24 Combine the right
8x = 36 Divide by 8
x = 36/8
x = 4.5
But x = AD