Step-by-step explanation
From statistics, we know the following relation:

Where:
• n(A) = # of elements in set A,
• n(B) = # of elements in set B,
,
• n(A U B) = # of elements in the union of sets A and B,
,
• n(A ∩ B) = # of elements in the intersection of sets A and B.
For this problem, we consider:
• n(A) = # of students enrolled in Elementary statistics = 82,
,
• n(B) = # of students enrolled in Business Calculus = 57,
,
• n(A U B) = total # of students = 100,
,
• n(A ∩ B) = # of students enrolled in both courses.
Replacing these data in the formula above, we get:

Answer
There are 39 students enrolled in both courses.