For nonempty subsets $F$ and $K$ of a nonempty set $V$ and a real valued function $f$ on $X\times X$ the notion of $f$-best simultaneous approximation to $F$ from $K$ is introduced as an extension of the known notion of best simultaneous approximation in normed linear spaces. The concept of uniformly quasi-convex function on a vector space is also introduced. Sufficient conditions for the existence and uniqueness of $f$-best simultaneous approximation are obtained.