The player in the eLearning course does not have this feature. However, you can right-click the video, download it, then play it in Elmedia or VLC Player (App Store).
Please click the link below for the instructions on how to change the playback speed for each player.
Keep in mind, during the lecture your student should be taking notes, and solving the example problems. Read the Instructions for Taking Notes in the eLearning course.