Recently I saw this theorem :
Assume that $A\leq B\leq C$ with $A\cong\mathbb{Z}^n\cong C$. Then $B\cong\mathbb{Z}^n$.
I wonder whether it is possible to generalise this result to arbitrary finitely generated abelian groups.
What I mean is this : If $A\leq B\leq C$ are finitely generated abelian groups with $A\cong C$ then $B\cong C$.
Using the fundamental theorem of finitely generated abelian groups it seems like it is true but I could not prove it.
Edit : If we remove the condition that $C$ is abelian then we know that the claim is not true for free groups. There are subgroups of $F_2$ which is not isomorphic to $F_2$ but contain a subgroup which is isomorphic to $F_2$. But I also do not know an example of a solvable group $C$ with there exists $A\leq B\leq C, A\cong C$ but $B\not\cong C$.