“…In recent decades, the topics related to the direct and inverse approximation theorems have been actively investigated in the Orlicz spaces and in the Lebesgue spaces with a variable exponent. In particular, for the Lebesgue functional spaces with variable exponent, similar results are contained in the papers of Guven and Israfilov [13], Akgün [2], Akgün and Kokilashvili [3,4], Chaichenko [8], Jafarov [14,15] and others. The latest results related to the Lebesgue spaces with variable exponent, and their applications are described in the monograph [10].…”