Transition from Strayer Upton to Jacob’s Algebra?

My son is just whizzing through the Strayer Upton book 2, ahead of where I thought he’d be, so I went ahead and bought book 3. I know that only some of the book needs to be used before heading into algebra (I want to use Jacob’s), but I’m not sure of what needs to be covered. I believe it was recommended that pre-algebra was unnecessary and this is all new territory for me. From looking at the chapters, it looks like I would want to cover the geometry sections as well as solving equations, ratios and proportions etc. From reading previous threads, it looks like some mentioned covering circles and equations but not much more was mentioned. If you have experience with this transition, please help!