Answer
n(AUB) = 33
Work Step by Step
In the question it is given that,
Set A contains 25 elements i.e. n(A) = 25
Set B contains 17 elements i.e. n(B) = 17
9 elements are common to both the sets i.e. n(A∩B) = 9
Now we need to find n(AUB).
n(AUB) = n(A) + n(B) - n(A∩B)
= 25 + 17 -9 = 42 - 9 = 33
