Final answer:
Rodney used the commutative property of addition to rewrite the expression (2x + 7) as (7 + 2x + 31).
Step-by-step explanation:
The property of operations that Rodney used is the commutative property of addition. This property states that the order in which numbers are added does not affect the sum. In this case, Rodney rearranged the expression (2x + 7) by swapping the terms to get (7 + 2x) and then added 31, resulting in the expression (7 + 2x + 31).
Learn more about Commutative property of addition