hey,

iits does not offer bsc courses on mathematics. undergraduate degree which is available in iits is bachelor of technology in various engineering stream.

however you can do msc in mathematics from iits. after 10+2 join bsc courses in mathematics in any good reputed college or institute. take preparation for iit jam exam to pursue msc courses from iits. iit jam is the entrance exam for master of science courses.

hope you may understand.