It is true that the answer of Rayappa Shrinivas Mahale is a method of converting Na wt% into mol% in NaCl. But the wt% -> mol% conversion is usually very difficult for EDX (or EDS). The concentrations of EDX analysis results are usually given by many elements' wt%. However some light elements (H, Li, Be, B,and sometimes C, N, ...) are not measurable by some EDS in air. The total wt% is 100% without including these undetectable elements. The first thing you must check is whether the wt% is correct or not the true results due to some assumptions in such a way that the analyte is made of only oxide, ...? Then you must follow the method of Rayappa Shrinivas Mahale