If $|G|=30$ and $|Z(G)|=5$, what is the structure of $ G/Z(G)$? The question is:
If $|G|=30$ and $|Z(G)|=5$, what is the structure of $G/Z(G)$?
I don't know what do we mean by 'structure' asked in the question. Please help.

$|G|=30$, $|Z(G)|=5$. $|G/Z(G)|=6$
We know that all groups of order 6 are isomorphic to $S_3$ or $\mathbb{Z} /6\mathbb{Z}$.
well known result:
If $G/Z(G)$ is cyclic, then $G$ is abelian.
If $G/Z(G) \cong \mathbb{Z} /6\mathbb{Z} $ ,then $G$ is abelian which is contradiction to $|Z(G)|=5$ . Therefore $G/Z(G) \cong S_3$ 
