From the given figure ΔABC, DE || BC.

Let EC = x cm.

We know that basic proportionality theorem states that if a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, then the other two sides are divided in the same ratio.

Then

⇒ x = 12 cm = EC

Here, AC = AE + EC

⇒ AC = 8 + 12 = 20 cm

∴ AC = 20 cm