Outcomes are the possible pairings of crust and pizza that Heather can choose. Based on the tree diagram, we see that there are 12 possible pairings starting from (thin, onions) to (pan mushrooms). Hence, there are 12 outcomes.
Based on the list of outcomes, there is only 1 outcome in which both the regular crust and sausage are chosen.
Lastly, for pepperoni OR mushroom being chosen, let's take a look and count.
There are 6 outcomes in which pepperoni or mushrooms were chosen.