The Commutative Propery of Addition states that rearranging the order of the numbers upon adding does not change the sum. For example, 2 + 1 and 1 + 2 are both equal to 3 or 2 + 5 and 5 + 2 are both equal to 7.
So, rewriting 15y + 4x using the Commutative Property of Addition is 4x + 15y. (Second Option)