Answer
25
Work Step by Step
By using the counting formula for finite sets:
$n(A\cup B)= n(A) + n(B) - n(A\cap B)$
By substituting:
$45 = 30 + 40 - n(A\cap B)$
$n(A\cap B)=25$
College Algebra (10th Edition)
by Sullivan, Michael
Published by
Pearson
ISBN 10:
0321979478
ISBN 13:
978-0-32197-947-6
Chapter 10 - Section 10.1 - Counting - 10.1 Assess Your Understanding - Page 687: 12
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