The discussion clarifies the relationship between the formulas SPI=EV/PV and CPI=EV/AC, showing that they are mathematically equivalent but serve different purposes. Rearranging these formulas allows for the calculation of one variable based on the others, depending on the available data. For instance, SPI can be used to find EV when PV is known, and vice versa. The confusion arises from the perception of having two solutions, but they are simply different interpretations of the same underlying relationships. Understanding these formulas aids in grasping the fundamentals of algebra in project management contexts.