Answer:
a. 4/52
b. 1/2
c. 1/4
d. 10/13
Explanation:
In order to obtain the probabilities, you have to apply the formula:

Where P(A) is the probability of an event A, n(A) is the number of favorable outcomes for the event and n is the total number of possible outcomes.
For part a:
The total number of 4 cards is 4, because there are four suits and a card 4 for each suit
n(a)= 4
n=52 (The total number of cards)
P(a)=4/52
For part b:
There are two suits with black cards and 13 cards in each suit. Therefore, the number of black cards is: 13(2)=26
n(b)=26
n=52
P(b)=26/52=1/2
For part c:
The total number of cards with diamonds is 13
n(c)=13
n=52
P(c)=13/52=1/4
For part d:
There are 3 face cards in each suit, therefore the total number of face cards is (3)(4)=12. The rest of the cards are none-face cards, therefore:
n(d)= 52-12 = 40
n=52
P(d)=40/52=10/13