Suppose you flip a coin and roll a number cube. What is the probability of having tails come up on the coin and an even number on the number cube?

Assuming a fair coin and a fair 6-sided die.

Coin has 2 sides with equal probability, 50% each.

Die has 6 sides with equal probability, 1/6 odds for each side.

Odds of heads = 1/2.

Odds of die rolling 5 or greater (5 or 6) = 2/6.

The probability of both things happening is the multiplication of the probability of the two happening separately, or (1/2) * (2/6) = 1/6.