But it is worth understanding the idea of solving
5026-
2819
----
????
by thinking of it as
2819+
????
----
5026
Yes and no. The concept is obviously important, so yes in that regard. But it's simple idea that doesn't need to be taught using four-digit numbers. It can easily taught by turning 8-3=? into 3+?=8. In this case, the concept is very easy to see because the calculation will be obvious to most students. Thus, they can focus on the addition concept without getting trapped in the details of the calculation (in which case they may not see the forest for the trees). So no in that regard.
As Master of None said in
another thread, educators seem to find ways to fail. IMO, this is one of them: take a straightforward concept that can easily be demonstrated by one-digit fact families or on a number line, twist it, and create something capable of confusing an engineer or a scientist.
