If you pick a card at random from a standard 52-card deck, what is the probability that it is either red or a 7?

The probability that the card you pick from a standard 52-card deck is 7/13. 

Let's first solve how many cards out of the 52 are red. 
Since half the deck is red and the other half is black, 1/2 of 52 is 26 cards. 

Next, let's solve how many cards you can choose with seven on it. 
Since there are four of each kind of card in a standard deck of cards, there are four sevens. However, we already counted the two red sevens when we solved how many red cards there are. So 4-2 = 2 cards. 

26 + 2 = 28 cards
28/52 = 7/13.

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