As usual, to master the art one has to try. Let's return to our first example . Many formulations are possible for a single problem. Here is a little different way to tackle the same problem. Forget for a moment about constants.
Many formulations are possible for a single problem.
In this case, the second equation is in fact the answer for one of the unknowns. Many formulations are possible for a single problem. Many formulations are possible for a single problem. We may learn a few things. First, there is much freedom in naming variables and putting equations together.