Summarize:

When you decompose a number into its various addends, you are breaking that number apart into different sets of other numbers (addends) that can be added together to get the original value. When one addend is subtracted from the original number, the second addend should be the answer you get. When both addends are added together, the original number should be the sum you calculate. This practice is easiest to do when you have a single digit number (a number that only has a "ones" place). You can combine the principles learned here with those learned in the "Decomposing into Hundreds, Tens, and Ones" section when you need to decompose larger numbers, but since there are so many possible addend combinations for larger numbers as a whole, this method would be impractical to use alone when working with large numbers. To decompose a number into its addends, all you need to do is write down all of the different possible ways of creating the original problem number using smaller numbers and addition. Example: Decompose the number 7 into its different addends. 7 = 0 + 7 7 = 1 + 6 7 = 2 + 5 7 = 3 + 4 7 = 4 + 3 7 = 5 + 2 7 = 6 + 1 7 = 7 + 0 For someone trying to learn this concept for the first time, it might be helpful to use visuals that demonstrate the process in practical, hands-on terms. Start with the original number of something. For instance, if the number is seven, you could start with seven jellybeans. Separate the pile into two different piles by pulling one jellybean to the side. Count the remaining jellybeans in the second pile and explain that the original seven have been decomposed into "one" and "six." Continue separating jellybeans into two different piles by gradually taking away from the original pile and adding to the second pile. Count the number of jellybeans in both piles with each move. This can be done with a number of different materials, including small candies, paper squares, colored clothespins, blocks, or buttons.
Understand the concept. Practice with a small number. Work through all the different addend combinations. Use visuals, if necessary.