All thirteen spade cards are removed from a pack of 52 playing cards. The remaining cards are shuffled and one is drawn at random. What is the probability that it is a red face card?

Removing the spades leaves 52 - 13 = 39 cards. Spades are black, so all 6 red face cards (jack, queen, king of hearts and of diamonds) are still there. $P=\frac{6}{39}=\frac{2}{13}.\frac{3}{26}$ is 6 out of the old 52; $\frac{3}{13}$ counts all 9 face cards left instead of only the red ones; $\frac{1}{13}$ counts just one suit's 3 face cards.