“…The fixed point method was used for the first time by Baker [9] who applied a variant of Banachs fixed point theorem to obtain the Hyers-Ulam stability of a functional equation in a single variable (for more applications of this method, see [5,6,13,14,15,16,42,66]). During the last seven decades, the stability problems of various functional equations in several spaces such as intuitionistic fuzzy normed spaces, random normed spaces, non-Archimedean fuzzy normed spaces, Banach spaces, orthogonal spaces and many spaces have been broadly investigated by number of mathematicians; for instance, see [7,10,11,18,21,24,25,27,28,35,39,40,49,50,53,54,55,69].…”