You will need to have basic knowledge about LaTeX language. The following link will show you the language you can use to type the equations you want: https://katex.org/docs/supported.html 

Secondly, for each equation you want to include, you will need to add the symbol $$ before the equation and at the end of the equation.

It is important to mention that math equations and formulas cannot be applied in the rubric section.

When setting up the instructions in the edit mode, you can add equations and formulas. As you can see in the example below, there are three formulas, all of them both starting and finishing with $$ symbol. 

Once you have finished setting up the instructions and have clicked Save, the overview of the instructions with the equations will look like this:

In the Interactive Document, when including a question you can also add an equation to it, again by starting and finishing with the $$ symbol. 

The following picture is an overview of how the equations will look after finishing the set-up of the question.

For the Interactive Video, the inclusion of equations is the same as for the Interactive Document. First, you need to choose, within the video, where to post a question. Then, when typing the equation you will need to open and end with the $$ symbol. Also, when choosing multiple-choice questions you can add equations in the possible answers.

After adding the questions in the Interactive Video, this is an overview of how the questions and the answers will appear:

While the video is playing, the question with the equation will appear as follows