This short list covers few sources of practice for Python, MATLAB, and R
Main source: official tutorial MATLAB Academy.
Bonus points for problems from MATLAB certification practice test.
Extra bonus points: online interpreter of Octave with functionality of shared coding. You can loop in another person to help you get through. GNU Octave is designed to be compatible with MATLAB syntax
Interactive Python exercises
36 exercises for learning Python. It does require having development environment set up, and might require someone to help you at the beginning.
R and RStudio
Swirl is a library that you run inside RStudio, that guides you through tutorial
There is also an interactive online tool, LearnR hosted on RStudio’s Github