The idea seems to be that they're teaching children to maths in their head rather than needing a piece of paper to work it out. The example is extremely odd tho

The idea seems to be that they're teaching children to maths in their head rather than needing a piece of paper to work it out. The example is extremely odd though, I can't imagine why you would go through that process in your head. I'd probably do something like: 12 = 2 + 10 32 - 2 = 30 30 - 10 = 20