The associative property states that you can add or multiply regardless of how the numbers are grouped. By 'grouped' we mean which we calculate first'. In other words, if you are adding or multiplying it does not matter where you put the parenthesis. Add some parenthesis(...) any where you like.

Adding 14 + 6 easily gives the sum of 20 to which we can add 7. The right hand side of the equation is where we add 14 and 13. Both sides will result in 27.