36 students in psychology (p)

28 students in statistics (s)

“of the students enrolled in the psychology class ,17 are also enrolled in statistics” ← this just means that the intersection of both the subjects are 17 students total.

so only psychology - 36-17 =19 students

only statisticts - 28 - 17 = 11 students.

Quantity A -

Total students in only one of each subject.

19+11 students = 30 = quantity B

Hence the answer is C

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Always deal with such problems using a Venn Diagram.

Hence C because 19+11=30

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thanks for this great representation of the solution

Thanks for taking the time to reply