I don't know anything about the math requirements for NASA, but I think the obvious answer is for you to just get better at math. I refuse to believe that doing so is beyond someone if they truly dedicate themselves to it and are passionate.

Also you're only in high school. You likely don't even know what you are capable of yet. In astronaut Scott Kelly's book he talks about how he was a pretty mediocre student in high school, but one day he joined a military academy and randomly became super motivated after reading a book about pilots. From that point on worked his butt of to get into the field. You don't need to be a genius now to one day work for NASA, but you should develop a plan now with steps to help you get there eventually if it's something you really want to do.