If you want to write mathematics examination you should again take admission into intermediate in the same college you have studied or you can even go for other colleges but going for same College will be best.

Now, you can eiher go for regular colleges or can even go for open universities. This is the way how you can again write maths examination or study in maths field. Can choose MPC or MEC. If you are choosing MEC you will again learn new subjects i.e., commerce and economics so going for MPC will be best