hi, need help.. use the atomic weight of carbon and chlorine to determine the theoretical value of the molecular weight of CH3OH(I've calculate the average mr of CH3OH -->0.39g/mol).(atomic weight: c= 12.0, cl= 35.5)

Your question makes no sense. Cl is not in CH3OH. The molar mass of CH3OH is 32 in round numbers. 12 + 3 + 16 + 1 = about 32.