molality is defined as moles of solute per kg of solvent
So, we need to find both the moles of solute and the kg of solvent.
moles of solute = 81.4 g x EG x 1 mol EG/62.1 g = 1.31 moles EG
kg of solvent = 1.50 L x 1000 ml/L = 1500 ml x 1 g/ml = 1500 g x 1kg/1000 ml = 1.5 kg
molality = 1.31 mol / 1.5 kg = 0.873 m