Constructing an Initial Basic Feasible Solution

and that the three demand constraints also sum up to this same expression. It follows that it is sufficient to work with any subset of 5 out of these 6 equations. To understand what this means more explicitly, suppose we are given a proposed solution to the original equations, and we are asked to check whether or not the given solution is feasible. To answer this, we would have to substitute the proposed solution into the equations one by one. Now, observe that if the proposed solution is verified to satisfy the first 5 equations, then the equality of the sum of the supply equations and the sum of the demand equations implies that the proposed solution must also satisfy the last equation. Moreover, it should be clear that this