Branch of Mathematics correlating with Physics 
I am taking a course in physics -- intro to modern physics and physics
  2 -- next semester, and the average weighted score, of people who took it in my university, is very low.
  I am wondering, which branches of Mathematics should I concentrate the
  most in order to do well in physics because I am going to take a lot more
  physics classes in the future. Of course calculus, but how about linear algebra,
  abstract algebra and so on? 

 A: If you take Calc III before Phys II, everything will make sense right away. In modern physics you should mainly encounter special relatively, quantum mechanics and statistical mechanics. Therefore a good understanding of ODEs, PDEs (especially how to set up boundary conditions), probability theory, discrete math (for stat mechanics), and some complex variables is essential. You might need linear and abstract algebra, but I doubt you will study Pauli matrices, Lie groups, etc. in intro modern physics class. One think for sure, you will do well in modern if you are good at integration and understand how to solve PDEs and set up boundary conditions. Special relatively just takes a while to get used to. Also, in quantum mechanics, you should encounter some tricky integrals, for example, Gaussian integrals, so knowing how to do them quickly should help. If you will not have time to take all of the aforementioned classes, I would recommend Theoretical Physics playlist on this YouTube channel. If you watch all the videos and understand each topic you should be fine.
