Your question is pretty obvious being a 12th class board student who has the burden to finish their syllabus before the board exam. See, there is not a fixed time to study maths in class 12th, but giving 2 hours every day is more than enough.
If you have a well organised time table that allows you to study for 6-8 hours per day, then I would recommend you to give 2 hours to Maths....
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