segment addition postulate

Author:
mike

how to find the length of a line segment given a congruent line segments length and the sum of both.

here is line ac. b is its midpoint. |--------------------|--------------------| a b c ab = 12 - (4/2) we know that ab + bc = ac (segment addition postulate). ac = 20 so 12 - (4/2) + x = 20. find bc. solve the algebraic equation. side note: we also know                  that ab = bc because they are congruent sides of a                    midpoint.