A full version program for Android, by Epsilon Development.

Learn how to do a long subtraction in a few minutes with this smart application. This app is designed to help people learn how to do math in a fast, easy, and effective way. The concept is simple: you are given a number and you have to subtract it from another number. The number you are given is a hint of the number you will get after the exercise. You have to do the exercise until you get the correct answer. 

This app is not only an educational tool, but also a learning aid. The learning aid is very useful for those people who have difficulties in doing math exercises.