There are 36 students in a class, and they all like at least one of the two sports, football and basketball. The number of students who like football is three times the number of students who like both sports, and the number of students who like basketball is four times the number of students who like both sports. How many students like both sports? 
Overseas Competition->Knowledge Point->Counting Modules->Inclusion-Exclusion Principle->Inclusion-Exclusion Principle for Two Sets