I feel like I let black people down

In every single one of my AP classes I’m the only black girl. I’m in AP calc, AP world, and AP bio and might take 2 APs next year. I’m the only black girl in every single one of these classes and they’re all filled with conservative white boys. I’m on par with pretty much everyone else in world and bio but I feel like the dumbest person in calc. You can’t really study for math classes you either get it or you don’t and just practise problems. Whenever the teacher calls on me my answer is always somehow wrong not because idk how to do it but because I always make the dumbest mistakes like forget to put a number or add correctly. I just feel like all the other white people are judging me in that class and I’m a bad representation.