A $18\%$ (w/w) aqueous glucose solution (molar mass $180\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$) has a molality of

In $100$ g of solution there are 18 g glucose and 82 g water. Molality is $n_2$ per kg solvent. So $m=(18/180)/0.082=1.22$ mol/kg. Using 100 g of solution as the solvent mass gives the wrong value 1.00.