Here's the question you clicked on:
creeperhug1441
Explain how applying the Associative Property of Addition to 7.5 + (2.5 + 4.9) makes it easier to simplify. Show the solution in your explanation.
Associative Property means you can move the parenthesis around and still get the same answer.
So, if you were trying to do this problem in your head, not using pen/paper/calculator, it isn't super-easy to add 2.5 and 4.9 inside the parenthesis. But it would be easier if the parenthesis was around two different numbers... two that are easier to add in your head.