There are 6 possible rolls from a standard dice, and 2 possible outcomes from flipping a coin.

Consider rolling a dice and then flipping a coin. How many possible combined outcomes are there?

For each dice roll, you could have flipped heads or tails, so there are a total of 6⋅2=12.

Next consider rolling the dice or flipping a coin. This time there are 6+2=8 possible combined outcomes.

We can generalize this to say that if event A has n possible outcomes and event B has m possible outcomes, then there are