It might be helpful to draw a diagram of a line in this case, but you could do this algebraically as well. The midpoint of any segment is basically the average of the two endpoints of the segment. Thus, for example, the midpoint of AC would be the value of A added to the value of C, which is then divided by 2 to get B. You just have to find all of the values for each of the letters, and then find the distance between B and D, for instance, which (the distance) may be represented as a system of equations with the statement of the distance for AE.