If you randomly select a card from a well-shuffled standard deck of 52 cards, what is the probability that the card you select is a club or diamond

I would use the theoretical method because each of the 52 cards is equally likely to be drawn.

There are 52 cards in a deck so there are 52 possible outcomes.
The event of interest is drawing a club or a diamond. There are 13 clubs and 13 diamonds. Add those up and that gives you 26 cards, which is the possible number of outcomes. knowing this we divide 26 by 52.

number of outcomes / total number of possible outcomes

26 / 52 = 1 / 2 = .5 = 50%

So the probability of this even is 1 out of 2 or you have a 50% chance of getting your club or diamond