If we know the mean number density of galaxies in the universe, the redshift z and the Hubble constant. Is it possible to find the mean distance between galaxies at such redshift? The redshift gives a ratio of two distances between the same pair of bodies, at two different time due to the expansion of the universe. I don't understand how is this parameter related to the mean distance between galaxies. And how is it related to Hubble's law anyway? The question is attached. All 3 parts are confusing me...Please show some approaching ideas or solution, thank you!