Now combine these two equations to make a new, third equation. We will do this using the "transitive property of equality", which states:
Transitive property of equality:
Whenever a=b and b=c, then a=c.
For our purposes, you might prefer to think of this the way Euclid (the famous ancient Greek geometer) phrased it: "If two things are each equal to a third, then they are equal to each other."