A system is a way of doing things - like algebra, A+B = C.
The inputs can change, but the formula stays the same.
When you don't know what what you don't know, you need a system to help you figure out what to do next.
In his book, A More Beautiful Question, Warren Berger offers us a system for bring "some semblance of order to a process that is by nature, chaotic and unpredictable."
Why + What If + How = Solution.
Here's an example from the book:
Person encounters a situation that is less than ideal: asks Why.
Person begins to come up with ideas for possible improvement/solutions - with such ideas usually surfacing in the form of What If possibilities.
Person takes one of those possibilities and tries to implement it or make it real; this mostly involves figuring out How.
Try the system out.
Test the results.
Tweak the inputs.
Try again.
Also...
Unrelated but just as interesting and pleasing... W(hole)+W(hole)+H(alf) is also the combination of intervals required to reach a major third above any tonic... it's a pleasing interval.