Bored Quantities If the variable X is added to the variable Y the sum is the quantity of X and Y X can not equal to Y ever So in theory if two different variables are added the sum outcome of the eqation will be the quantity of both variables and will NEVER equal to one of the two variables You say X Y Z Z never Equals X Z never Equals Y It s faulty X 0 Y 1 So X Y Z 1 therefore Z Y hehe C What you meant to say is If any two variables X Y X Y 0 are added the sum will never equal any one of the two variables D But what if we take a person with 3 different ancestries In theory if one has 3 different ancestries they are never just one of the ancestries however you would qualify such a statement So X Y Z A A can never equal X Y or Z Of course here we d have to add the condition that X Y and Z must be 0 Whereas in Example C the variables just can not equal 0