Answer
Blair uses the distributive property
Work Step by Step
Blair uses the distributive property to find:
$$ 400+20-20-1 \\ 400-1\\ 399$$
Here, we see that the Math becomes much easier for Blair to do in his head.
Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)
by Bittinger, Marvin L.; Ellenbogen, David J.; Johnson, Barbara L.
Published by
Pearson
ISBN 10:
0-32184-874-8
ISBN 13:
978-0-32184-874-1
Chapter 4 - Polynomials - 4.6 Special Products - 4.6 Exercise Set - Page 277: 105
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