bi(two)...sector(section). Bisector cuts the segment into two equal sections.
BC = CD <em>definition of perpendicular bisector</em>
BC + CD = BD <em>segment addition postulate</em>
CD + CD = BD <em>substitution</em>
2CD = BD <em>added like terms</em>
2CD = 16 <em>substitution</em>
CD = 8 <em>division property of equality</em>
CD = y + 3 <em>given per graph</em>
y + 3 = 8 <em>transitive property</em>
y = 5 <em>subtraction property</em>
Answer: 5
