We have in this problem four unknowns to be determined, K, X, Y and Z.
In general, one has much more than four observed galaxies, and the resulting
system of equations turns out to be overdetermined (more equations than the
number of unknowns). This is a rather common situation in astrophysics. For
example, a binary stellar system can be spectroscopically observed in many
orbital phases yielding a set of observations much larger than the number of
unknowns of the problem (orbital inclination and eccentricity, mass ratio, etc.)