hey,

i hope you are good

no , there is no any entrance exam conducted by delhi university for the admission in B.Sc hons mathematics , in this course admission is provided on the basis of merit delhi university releases every year , your 10+2 score would be enough to get admission in the same course.

for more information you may refer to the link mentioned below

https://university.careers360.com/articles/du-courses

good luck!