How to quickly reinforce basic math skills?

Question

Mathematics

Good afternoon, for certain reasons, I decided to learn math.
Now I'm taking courses / reading short books with examples like I.S. Sominsky "METHOD OF MATHEMATICAL INDUCTION"
I'm ashamed to admit, but I don't understand a number of examples at all, or rather, the way the author came to such a decision - reducing / opening brackets, etc. More precisely, after sitting for a couple of hours, it will dawn on me, but it takes too much time.
I tried to refresh school knowledge in mathematics, but all the examples are simple and I understand them, but there are no complex examples, on the other hand, more complex material already implies some skill in this regard.
Is there any course or better "pocket" reference book of 40-50 pages (like Solominsky) with a concise explanation of the rules of elementary mathematics and solving complex problems (of particular interest is the reduction / expansion of various formulas) and tasks on which to hone skills?

Answer 1

Why do you need it?
Scanavi is not needed. It will be difficult. Take ordinary school textbooks and solve the bulk of the problems. Ask questions if you can't catch something. This will be enough