Question

which mathematical property is demonstrated? If x = 3 and -3 = z then x = z

Answer 1

Integers. Most likely, or opposites I suppose.

Answer 2

or isolated variables.

Answer 3

It's called the transitive property.

http://www.mathwords.com/t/transitive_property.htm


I see no way to tell you this without it looking like a direct answer. Such questions are hard to explain and there is no way to properly let you know the answer without you knowing the actual concept.