For the Pair of Similar Triangles, Find the Length of the Indicated

Multiple Choice

For the pair of similar triangles, find the length of the indicated side.
-In the outer triangle, the shortest side has length 12 , and the middle side has length 15 . In the inner triangle, the shortest side has length 4 , the middle side has length 5 , and the longest side has length 6 . Find the length, $x$ , of the longest side of the outer triangle.

A) $x = 20$
B) $x = 18$
C) $x = 6$
D) $x = 24$