Adding unit fractions

The app proposes 21 challenges to overcome. Obtaining the proper fractions listed at the top of the application, adding two or three unit fractions. Each proposed proper fraction has a variable number of solutions. And different levels of difficulty You can not repeat unit fractions with the same value. In the app you'll find a button to delete all the solutions found in the current problem, and to start from scratch. The littlest unit fraction used in this app is 1/28. The program is designe