I don't know if it will help your test scores, but I found the 3Blue1Brown Youtube channel to be incredibly helpful in learning fundamental linear algebra and calculus. My interest in learning this was for 3D game development in Godot, but math is math I suppose. Around the same time I hit up my local library and checked out an "outdated" college textbook on calculus (which was also great, but I had to return it too soon).

I generally prefer literature over video content, but these video series have absolutely fantastic visual representations of the concepts being explained. I think they are a great place to start before dipping into more rigorous literature. You must consider that the traditional way of teaching mathematics is on a chalk board, which is ultimately a visual medium.