Self Teaching myself Machine Shop Math from book Technical Shop Math by Thomas Achatz. According to the examples given, a=a is a Reflexive Property while a+b=b+a is described as a Commutative Property of Addition. The quiz question is: Name the property illustrated in the example. a) x+1=x+1. My answer is this is a Commutative Property of Addition. The book claims the correct answer is a Reflexive Property. Can anyone explain why my answer is incorrect, Please. Thank you.