Hi there,
Properties of Equality is two equations that have the same solution which are called equivalent equations. For example: 5+3=2+6 which all equal to 8.
In geometry, properties of Equality are the reflexive (2x=2x, a=a, b+1=b+1), symmetric (2a=3b then 3b=2a) and transitive property (if a+1=3 and 3=1-b, then a+1=1-b)
Hope this helped :)
Have a great day