Just to clarify.. is she is a CC compressed Math 8, Algebra I class combined? If so.. Math 8 isn't "pre-algebra" it is pre-algebra the first 4-5 chapters of Algebra & some gemoetry. Thus starting "Algebra book" would be getting into 2-equations and two unknowns. Still sounds like they have skipped a bunch of important information.
Are they teaching the cookie cutter approach to math? What I mean by that is not really explaining how or why it work but just showing them here is technique A,B, and C to solve the problems.
I agree that your daughter probably needs more practice and understanding for solving for one equation before she gets to two equations.
My only suggestion for understanding two equations & two unknowns then uses graphs? Solve with graphs first. Graph the equations & see where they overlap. IMO this is one of the best ways of understanding what is going on. Graph lots & lots of different equations. Graph them on top of each other and see where they intersect. Graph the different steps, so you can see that equations that look different are really equal.
