The way you punch commands into a 10 key calculator differs slightly from the way you would use a standard calculator. 

By nature, 10 key calculators are designed to add, thus if you want to subtract, you must add a negative number to the equation. 

Quick tutorial to learn how to use the 10-key keypad in just a few minutes (and become proficient in less than an hour)

The Basics:

- Enter the number that you want to start with into the keypad. 

- Press the "+" key. 

- Enter the next number, if you are adding. If you are subtracting, press "-" then enter the next number. 

- Press "=" to get the result of the equation.