Theorem 2.2 previous knowledge expectations?

[amukina]

I'm currently in the same mind set as #13.

I have no previous mathematical experience. I was happily reading along the first chapter excited at the presentation and finally understanding dots you were connecting. Right up until the very top of page 16.
"If we solve for a₀ in the first equation, we get a₀ = 3 - 2a₁" and all I could think was "do we?". I've re-read this section on three separate days now and I can't find any path that would lead me to this result based on information given, let alone everything that comes after. At best I might have thought: a₀ + a₁ * 2 = 3 could solve to a₀ = 1, a₁ = 1, 1 + 1 * 2 = 3. The simplest possible calculation I know how to make, and it would obviously fall apart for the second equation.

In #13 you mention we don't need an understanding of every concept before moving on, which goes against page 10 that explicitly says "the unspoken rule is that the reader should not continue unless the reader understands what the definition is saying". So I'm not sure what to feel. Is the expectation I already have an understanding of this, or did I clearly overlook an explanation somewhere?