A card is drawn at random from a deck. what is the probability that it is an ace or a king?

There are 52 cards. Of this, there are 4 aces (one of each of the four suits) and 4 kings. There are 4+4 = 8 cards that are either an ace or a king (but not both). Note that the events "drawing an ace" and "drawing a king" are mutually exclusive. Being mutually exclusive means its impossible to have both events occur simultaneously for any single card.

So there are 8 cards we want (ace or king) out of 52 total

Dividing the two values, and reducing fully, gives:

8/52 = (4*2) / (4*13) = 2/13

The final answer as a fraction is 2/13