which branch is better to opt in iit, mathematics and computing or electrical engineering what should be preferred
Hello. It completely depends on your interest. Check where you can excel perfectly.
Mathematics and computing or electrical engineering, both hold a very good future.
Computing will hold a logic which will need more logical expressions to be solved.
Whereas for electrical you will have to deal with circuits and will be more numerical based. You will have to perform each practical single handedly because that will require self knowledge and practice.
So choose where you can perform better and most importantly about what you are ambitious about.
Hope that helps!