The commutative property of addition tells us that the order in which 2 numbers are added does not change the sum of those 2 numbers.  In the earliest level we can also predict that the objects in two sets will give the same sum when combined regardless of which items we count first.  Examples of this property follow.

+    =       +

  +    =       + 

  1  +  7  =  7  +  1    

  2  +  6  =  6  +  2    

                                            3  +  4  =  4  +  3

4  +  5  =  5  +  4

6  +  3  =  3  +  6

7  +  2  =  2  +  7

8  +  1  =  1  +  8

9  +  0  =  0  +  9