Answer:
The length of AC = 25
Explanation:
Triangle ABD is a right triangle and can use the Pythagorean theorem which is
+
=

one leg is BD = a = 12
hypothenuse is BA = c = 15
other leg is AD = b, which we need to find
+
=

=
-

=
-

= 225 - 144
= 81
b = leg AD = 9
The length of AC = AD + 16 (given in picture) = 9 + 16 = 25
I hope this helps