How do i use the associative property?

Answer 1

It just means that if you have a string of additions (or multiplications) you can pick any two adjacent numbers and add them first, without changing the result.

2+5+3+6 can be done as
(2+5)+3+6 = 7+3+6 = (7+3)+6 = 10+6 = 16
or
2+(5+3)+6 = 2+8+6 = 2+(8+6) = 2+14 = 16

You can put parentheses around any par of numbers and do that addition next.