What is the ruler postulate?

The distance between two points can be determined by the
the absolute value of the difference
of the real number values of the two points.

OR
What is the ruler postulate?

The distance between two points can be determined by the
the sum
of the real number values of the two points.

or
What is the ruler postulate?

The distance between two points can be determined by the
the absolute value of the sum
of the real number values of the two points.
or
What is the ruler postulate?

The distance between two points can be determined by the
the difference
of the real number values of the two points.