If you are a teacher, you definitely have an e-mail in your account because this step is part of the activation process.
For the students, the e-mail is not mandatory to create an account. Therefore, it might be impossible to reset the password. To avoid that unfortunate situation, we recommend specifying recovery e-mail in every student account. Here is an article that explains how to do it!
First, select the "forgot password" link on the login page
That will lead you to a simple form that allows you to reset your password using the e-mail address that is linked to your account!
From there, follow the instruction to reset your password and have fun using Netmath again!