Welcome Sophia.
Here is some help. Not your actual total Project but it is a Block example.
If textbox1 contains the total bill (25) and textbox2 contains the number of people sharing (4) then label1 equals each's share (6.25)
Since you didn't understand something in your lectures and have been turned loose to fend for yourself, here are some resources to help you learn to use the AI2 tools. I recommend you read the book in the link below. It has coding examples.
Try to code something; then post YOUR Blocks here and someone should give you specific advice. 
Good luck.
A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here Course In A Box and the aia files for the projects in the book are here: App Inventor 2 Book: Create Your Own Android Apps
How to do a lot of basic things with App Inventor are described here: How do you...? .
Also look here App inventor español. Offline. Tutorial. Ejemplos. Instalación. Códigos. Juegos. Curso gratis de App inventor. and here Tutorials for more tutorials including Imagnity.com List Tutorial, Mirrored - @Saj
Learn about components Component Reference
and visit the Library The MIT App Inventor Library: Documentation & Support Help>Library on the MENU