Fox cartoons refers to animated television series presented by the American TV network Fox Broadcasting Company. During the more than thirty-year existence of the Network, there have been many successful prime time animated series and Fox cartoons. The first and most famous of these, "The Simpsons", was the first such series since the end of "The Flintstones" in the 1960s.
The Flinstones were on Fox cartoons before The Simpsons
It states that The First and most famous was the Simpsons, so it is given that the Flintstones were not a fox cartoon. it fooled the system as it mentions that the simsons did indeed come after the flintstones.