This algebra video tutorial provides a basic introduction into functions. It contains plenty of examples and multiple-choice practice problems as well as free response problems.
Functions - Free Formula Sheet: https://www.video-tutor.net/precalculus-formula-sheets.html
Functions - Video Lessons:
https://www.video-tutor.net/functions.html
Final Exam and Test Prep Videos:
https://bit.ly/41WNmI9