A free app for Android, by Overpass Apps : Super-Human Apps and Games.

The Learn Algebra Bubble Bath Game is a great way to improve your algebra skills while having fun. The concept is quite simple and intuitive: You need to pop all the bubbles by solving the given equations. The more difficult the equation, the harder it is to pop the bubble. So the more you improve your algebra skills, the more difficult the game becomes.

To play, simply open the game and start popping bubbles. Each category will have 10 levels, and the difficulty will increase as you go from level to level. So it is easy to start with the easy categories and work your way up.