Inner Algebra ↑
agens в посте Metapractice (оригинал в ЖЖ)
How To Do Algebra In Your Head
Aaron Maxwell
Many mathematicians and engineers can look at an equation, think a moment, and know its solution. Some can do very complex math this way. Most people can learn to do this. By using certain mental abilities you have in ways described in this book, you can do things mathematically that may have not seemed possible before.
In this book, we focus on algebra; you learn to solve algebra equations mentally. It is necessary that you have already learned algebra in some way (probably through a math course)...
http://hilomath.com/inneralgebra/html/