Answer:
46 units
Explanation:
The diagonals of a rectangle bisect each other, which means that in this case, AE = EC. So, set the two expressions equal to each other and solve for x:
6x - 55 = 3x - 16
3x = 39
x = 13
Now, another property of rectangle diagonals is that they're the same length, which means AC = DB. So, let's just find the length of AC:
AC = AE + EC = (6 * 13 - 55) + (3 * 13 - 16) = 23 + 23 = 46
Thus, since AC = DB, we know that DB = 46 units.
Hope this helps!