Oh reminds me of something peculiar. I gave math lessons to a 16yo guy. Mainly quadratic root formula. He understood the "high level" bits, but he failed so often at basic algebra after plugging the coefficient into the formula that he felt completely demotivated. It was odd to try to explain to him that he got the idea right, but failed at the basics. I told him that to mean "you can do the hardest, you will be able to get the easiest" but he interpreted it at "whats the point if you cant do the low level bits" ...