What is the total number of orbitals associated with the principal quantum number n = 3?

Actually the third shall is composed of 1 s orbital, 3 p orbitals, and 5 d orbitals. Each of these orbital holds 2 electrons therefore the total number of electrons are:

(1 + 3 + 5) * 2 = 18

There are 18 electrons that can fall in the 3rd shell. And there are 9 orbitals.