2. In triangle $A B C$, a point $D$ is taken on side $A C$. It turns out that $A B>B C=6$, $B D=7$, and triangles $A B D$ and $B C D$ are isosceles. Find $A C$. If there are multiple answers, list them in any order separated by a semicolon.
Answer: $12 ; 13 \| 13 ; 12$