Since there are 52 cards in a deck, you can deal 10 poker hands (50 cards) and there are 2 cards left in the deck.
If you are asking in how many ways can a poker hand be dealt then your answer is `(,)=(52cdot51cdot50cdot49cdot48)/(1cdot2cdot3cdot4cdot5)=2598960`.
Probability of getting 4 kings:
Probability of event `A` can be calculated as `P(A)=N_A/N` where `N_A` is number of different occurrence of event `A` and `N` is number of all possible outcomes. So probability of getting 4 kings can be calculated as quotient of number of different hands with 4 kings and total number of different hands which is, as stated above, `(,)`.
Let's now calculate number of different hands with 4 kings:
Since there are only 4 kings in a deck we can't choose anything, we must take them all. For the 5th card in our hand we can chose 1 from 48 remaining cards. Thus there are only 48 hands with 4 kings.
So probability of getting 4 kings in a hand is