Direction (66-70): What should come in place of the question mark(?) in the following number series?

729, 243, 81, 27, ?

In the following questions two equations numbered I and II are given. You have to solve both the equations and ____
I.$$ {7\over \sqrt {x}}+{5\over \sqrt {x}}=\sqrt {x}$$
II.$${y^2 - {12^{5/2}\over \sqrt {y}}}= 0$$
Give answer
(A) x > y
(B) x ≥ y
(C) x < y
(D) x ≤ y
(E) x=y or the relationship cannot be established

Directions : What will come in the place of the question mark (?) in the following number series?

60.75, 40.5, 27, 18, 12, ?

Directions : What will come in the place of the question mark (?) in the following number series?

1  2  6  15  31  ?