Manish, LLB is a 3 year Bachelor course which is pursued after 12th in any stream. It can be also pursued after B.Sc Mathematics but you cannot skip the first 2 years and then join the 3rd year directly. There is no such lateral entry option. This is because what you are taught in B.Sc Mathematics and what you will be taught in LLB are different and there is no similarity between these 2 courses as the outreach is also different. So should you be willing to take up LLB, you should start based on your 12th qualification and not on your B.Sc qualification. AP LAWCET, TS LAWCET, MHCET LAW are few entrance examinations that are conducted for admission to 3 year Law programmes. This is the same even with 5 year Integrated courses, You cannot join the 4th year directly because you have completed your B.Sc. That is not a feasibility. For both 3 year LLB and 5 year Integrated Law courses, you have to take a detour, appear for the entrance examination based on your 12th and start again. Unfortunately, this is the only way for you to start a career in Law.