I'm somewhat concerned about my abilities in math lately. I'm a physics student and over the summer I've begun studying to maintain my knowledge from last semester. However, I keep running into difficulties of many kinds. Firstly, I make stupid math mistakes. Like kindergarten stuff. To begin my summer studying I started with khan academy, doing some simple average rate of change questions. I kept doing things like saying that 32-8 is equal to 16. It was so strange. I'm pretty sure it's just because I'm not focused. I haven't really dedicated myself to studying and I only just started today so it's natural that I'd be out of it. It put me off though.

Secondly, I'm still struggling with concepts from years ago. Geometry for example. Khan academy asked me to find the maximum area of an isosceles triangle. I had no idea where to start, largely because I don't know what an isosceles triangle is.

In essence I'm asking: Would it be best for me to go back and study my high school fundamentals first and then move on to calculus when I'm ready or should I keep going and hope to pick those old skills up along the way?