This free app will work on android TABLETS and PHONES. Subtraction Level 1 is the ductory version of a program to teach subtraction. The program contains: a] several very basic examples to demonstrate the process of subtracting. These exercises are accessible by menu; B] subtraction tables – subtracting the numbers: "1"; "2"; "3", "4"; "5"; "6"; "7"; "8" and "9".