AB = 18, CD = 8
Tells us that C is midpoint of A and B. There is one more possibility that A and B lie on same point but which is not true as given that AB = 18. So AC = 9, CB = 9
But question asks about distance between BD. Now D can be left of C or can be in right of C, so you cannot say for sure what is distance between BD. So this alone is not sufficient.
This tells us about A is on left of D, but does not give any information about B, & C. So this alone is also not sufficient.
Combining both statement are not going to help either. Because although A is on right of D, but C can be on left or right of A. Depending on C is in right or left of A position of B will also change. So no fixed distance between B has D.