At some point in your Excel ventures you will come across the #DIV/0 excel errors. what I will tell you is as errors go its a simple fix, however he the problem comes from your logic.
How does it happen?
If you remember arithmetic you should recall when doing divisions, you you divide anything by Zero (0) what will you get?
The Reason is:
That is right, you cannot, it is not mathematically possible as there is no answer, therefore Excel will give you and error.
From that it means you need to examine your logic, with the cells because the one of them contains a Null value (empty) or a zero.