Originally Posted by Val
Originally Posted by 22B
Converting a-b=? to b+?=a is quite sensible (as long as the stuff you wrote on the side can be done as mental math without writing it).

It must be written down. In a certain way that involves drawing boxes.

Okay, the rigid setting out requirements, and the remedial level, are ridiculous, I agree. But it is worth understanding the idea of solving

5026-
2819
----
????

by thinking of it as

2819+
????
----
5026