We have 13 spades in a standard pack of cards.
Let's take cases.
Case 1: First card -- spade
Our sampling space is 52 cards, it isn't changed because we still haven't drawn anything.
Taken that it's a spade, our sampling space is reduced because it is dependent of our first event.
Case 2: Second card -- spade
Given that we don't replace the card, the second card is dependent of the first card. If we pick up a spade on the first draw, we have 51 cards to choose 12 spades.
(ie 4/17)