Which is an example of the associative property? a) x + 5 = 5 + x b) (x + 3) + 7 = x + (3 + 7) c) 3 • (x + 5) = 3 • x + 15 d) if x = a, and a = 7, then x =

The first thing we are going to do to solve the problem is to define what associative property is:
 Associative property Property that is fulfilled if, given any three elements of a given set, it is verified that there is an operation that verifies equality
 An expression that meets the definition is:
 (x + 3) + 7 = x + (3 + 7)
 We observe that both members of equality are identical, but written in different ways.
 
 B) (x + 3) + 7 = x + (3 + 7)

It is going to be the third choice