A pyramid of biomass is the amount of energy contained in biomass, at different trophic levels for a given time and higher trophic levels would have less total biomass than those below, because some energy is lost in the transfer from one level to the next. Thus, the amount of biomass at all trophic levels cannot be equal.
A pyramid of numbers represents the number of organisms in each trophic level. For upward pyramids, the bottom level would be of quite large organisms. But sometimes the pyramid of numbers might be inverted. Then, the number of organisms at lower level would be less than that at higher level. Thus, the number of organisms at all levels also cannot be equal.
An ecosystem is made up of all the living animals and plants and the non-living matter in a particular place, like a forest or lake. All the living things in an ecosystem depend on all the other things - living and non-living for continued survival - for food supplies and other needs.
Thus, a balanced ecosystem is one in which the amount of energy synthesized and utilized is nearly equal.