LOF algebra mastery?

Is the gist of your question how do you know if using LOF your child has mastered algebra? Personally, we use MUS alongside LOF even though I think it could be a stand alone curriculum for some kids in the later volumes. My son is in algebra and seems to really get what he is learning from Fred. My dd is in pre-algebra and I feel she needs more explanation and practice than it gives. I don’t really have a standard for mastery; I just can tell when they are really understanding or not.

Nebby