Hello,
you can ask questions about homework assignments, but have a look at this page to see, what would improve your question.
To get meaningful answers, it is always a good idea to post some data (which can be done with dput(MYDATA) or, if you want to share just a tiny bit, dput(head(MYDATA, 50))). You should also share the code you tried so far, just to get an idea where your problem occurs (e.g. are you using base R oder ggplot2 to create your histogram?).
Consider editing your answer or post further informations in the comments.
Kind regards