Question

give an example on an addition problem in which you would and would not group the addends differently to add

Answer 1

Addends are any of the numbers added together in an equation. 

The only time their grouping would matter would be if there were parentheses used to alter the normal Order of Operations. 

For ex:
2 - (8 + 3)  here, the 8 and 3 have to be grouped together before doing the subtraction.

Any addition problem without parentheses can be used for one where the grouping doesn't matter