Todo Math is optimized to set different languages for different users.
To change the language, follow these steps:
1) Open the app.
2) Select a profile.
3) Tap on the bar at the top of the page with the user's name in it to access the My Info page.
4) Under the Settings heading on the right side of the screen, you'll see the current language listed. Click on the language button to select from all of the available language options.