Answer: CB=3
Step-by-step explanation: Parallel lines are lines on the same plane that do not intersect. We know that there are five lines listed, but we can ignore line AD because point A was only mentioned once and is not apart of the parallelogram. So focusing on the other lines we can infer that line DC is parallel to line BE, because lines CB and DE are parallel. So given that line DE=3, than line CB=3