hi,

 ISI is the most prestigious institution to study b.math and b.state. from the beginning of 10+2 you need to clear your basics of matematics. questions will be from basic 10+20math and secondary mathematics. if you also prepare for iit jee it will be an added advantage. how ever isi b.math test will be only on mathematics. there is a book called tomato , which has all previous years bmath questions. solve this book thoroughly. hope it helps.