Answer:
hope it helps you
Step-by-step explanation:
Let
A be the set of students in art class
B be the set of students in dance class
n(A) = 35
n(B) = 57
a) When 2 classes meet at different hours and n(A ∩ B) = 12 we have:
n(A ∪ B) = n(A) + n(B) - n(A ∩ B) = 35 + 57 - 12 = 80
b) When two classes meet at the same hour we have A∩B = ∅ that is n(A ∩ B) = 0 and
n(A ∪ B) = n(A) + n(B) - n(A ∩ B) = n(A) + n(B) = 35 + 57 = 92
