Proof: We are given that AB is equal to 12 and AC is equal to 6 Applying the segment addition property, we get AC plus CB is equal to AB Applying the substitution property, we get 6 plus CB is equal to 12 The subtraction property can be used to find CB is equal to 6 The symmetric property shows that 6 is equal to AC Since CB is equal to 6 and 6 is equal to AC , AC is equal to CB by the [Dropdown 1] property. So, line segment AC is congruent to line segment CB by the definition of congruent segments. Finally, cap c is the midpoint of line segment AB because it divides line segment AB into two congruent segments.