Answer:
DC=3 units
Step-by-step explanation:
From the given figure, it can be seen that DE is parallel to BC, thus by using the basic proportionality theorem, we get
AE/EB=AD/DC
⇒12/4=9/DC
⇒DC x 12=9 x 4
⇒DC x 12=36
⇒DC=36/12
⇒DC=3
Thus, the length of DC will be =3 units.
hope it helps:)