Abstract:
Considering two subgroups $A$ and $B$ of a group $G$ and $\varnothing\ne X\subseteq G$, we say that $A$ is $X$-permutable with $B$ if $AB^x=B^xA$ for some element $x\in X$. We use this concept to give new characterizations of the classes of solvable, supersolvable, and nilpotent finite groups.
Keywords:Sylow subgroup, supplement to a subgroup, maximal subgroup, nilpotent group, supersolvable group, solvable group, $X$-quasinormal subgroup.