The freezing point depression is 0.50°C, so the molality of the solution is 0.50°C/5.12°C = 0.098 m.

Then the number of moles of the solute is 0.098 mol/kg * 0.036 kg = 0.0035 mol which corresponds to 0.64 g of adrenaline. Finally, the molar mass of adrenaline is 0.64/0.0035 = 183 g/mol.