36.69 g/100 ml is the solubility of NaCl at 50oC. You would have to look this up in a table.
To obtain % by mass, you take the mass of NaCl divided by the total mass x100%
Density of H2O at 50o is about 0.988 g/ml
Thus 100 ml H2O at 50o = 100 ml x 0.988 g/ml = 98.8 g
Mass NaCl = 36.69 g
Total mass = 36.69 g + 98.8 g = 135.49 g
mass % NaCl = 36.69 g/135.49 g (x100%) = 27.1% (to 3 significant figures)