Scientists from Stanford University in the USA studied how a person solves mathematical problems and found out that adults use the skill to "get" answers from memory based on past experience.
Why do teachers insist on regular attendance of lessons? It's not their harmfulness, but the fact that when solving mathematical problems, we "get" answers from memory based on past experience. And in order to consolidate this experience, you need to repeat the material and train in solving examples. This is the only way to remember all the rules and formulas