Answer: 1/13
Step-by-step explanation
There are 4 copies of "3" in a deck of cards. There's one card per suit (hearts, diamonds, spades, clubs). There are 52 cards total.
The probability is 4/52 = 1/13
If we focused on a particular suit, say the diamonds, then there's one 3 of diamonds out of 13 diamonds total. That leads to 1/13