There is an unambiguous connection between the period of the change in the brightness of the Cepheid and its luminosity. By measuring the period of change in the brightness of the Cepheid, you can establish its absolute stellar magnitude, then, based on a comparison of the apparent and absolute stellar magnitudes, you can determine
distance to the Cepheid.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.