Abstarct: One of the main topics of Best Approximation theory is the determining of the proximinality of subsets from a space. since this is a subject in some sets it's hard, we try to reduce the scope of our review to make the process easier. Indeed in this research, instead of determining the Proximinality of the entire set, focos on the Unit Ball of set. Also, one of the newest topics of Best approximation theory is the strongly proximinality spaces, which we introducing, and we say The relationship between this spaces with the Hyperplanes an the Best simultaneously approximation theory.