[sammoth]

But is Khan Academy really so different to formal training? I mean, who is going to understand a Khan Academy video on solutions to 2nd order linear homogeneous differential equations if they have never learned any algebra? There is language in there that is necessary to explain it that they will have had to learn before.

It would be great for there to be more resources for learning maths outside being officially enrolled in formal education, but I don't think this has anything to do with the language used in mathematics being too terse or obtuse. Lots of good undergrad textbooks are no less understandable than a Khan Academy video, try those instead of Wikipedia.