Given:

Solution:
Here, we need to find the property illustrated by this equation.
It the given equation, we write (x+y) as (y+x).
According to the Commutative Property of Addition, if a and b are two real numbers, then

It means, Commutative Property of Addition is illustrated by the given equation.
Therefore, the correct option is b, i.e., Commutative Property of Addition.