Here, with respect to boys
Swimming + Running = 50% + 70% = 120%
The extra 20% is meant for the boys who opted both swimming and running.
Similarly, with respect to girls
Swimming + Running = 80% + 60% = 140%
The extra 40% is meant for the boys who opted both swimming and running.
In pictorial representation:

So, percentage of people who opted for both swimming and running = 20% boys + 40% girls

The question is "In a group of 250 students, the percentage of girls was at least 44% and at most 60%. The rest of the students were boys. Each student opted for either swimming or running or both. If 50% of the boys and 80% of the girls opted for swimming while 70% of the boys and 60% of the girls opted for running, then the minimum and maximum possible number of students who opted for both swimming and running, are"

Hence, the answer is '72 and 80, respectively'