You flip a coin and then roll a fair six-sided number cube. what is the probability the coin lands heads-up and the number cube shows a number 3?

Flipping a coin is a 50% chance for heads or tails already which can be represented as 1/2. Rolling a six-sided dice gives a probability of about 17% or 1/6. You would NOT add up the fractions but multiply them, 1/2 * 1/6 would equate to 1/12. There is a 1/12 chance of flipping a coin heads-up and the number cube showing 3 (or about 8% when rounded).