In the quiz, it asks
Another measure of fairness is equal opportunity, which means that those members with a property should have equal probability of a positive prediction, but not necessarily those without that property. Suppose that the ability to fly is meaningful to the prediction, and other properties are not considered. Your model predicts a positive result for 10 of the 80 Elephants which can’t fly, and 15 of the 20 Elephants which can fly. If there are 40 Flamingos which can’t fly and 60 which can fly, which of these are valid numbers of positive predictions under equal opportunity:
The answer explains
As 3 of 4 flying Elephants had a positive prediction, 3 of 4 flying Flamingos should have one too.
Why are flightless flamingos not considered here ?