Answer:
D. 15
Step-by-step explanation:
Let the missing length be represented as x.
Thus:
(24 - x)/12 = x/20 => angle bisector theorem
Cross multiply
20(24 - x) = x(12)
480 - 20x = 12x
480 - 20x + 20x = 12x + 20x
480 = 32x
480/32 = 32x/32
15 = x
Missing length = x = 15
