that: if the coordinates of the points are a and b, then AB equals the absolute value of a minus b equals the absolute value of b minus a ??? ??? ??? Segment Addition Postulate If R,P, and Q are three points on a line and R is a point between points P and Q, then PR plus RQ equals PQ ??? ??? ??? Betweenness Postulate If R,P, and Q are three collinear points and PR plus RQ equals PQ, then R lies b