List the numbers in an organized fashion. Writing all the numbers horizontally or vertically on a clear piece of paper is an easy and convenient method for this. For example, if you have the numbers 79, 40 and 95, write them in a manner like so:
79
40
95
Add the first two numbers together. In the example, 79 + 40 yields 119. For larger numbers, you may require a calculator to perform this addition.
Cross out the first two numbers and replace it with the new number. You now have a "new" list of numbers. For this example, you would have the new list:
119
95
Repeat the previous two steps until you only have one number remaining. This is your net unit sum. For the example, you would only need to repeat the addition step, yielding 119 + 95 = 214.