#### Answer

4

#### Work Step by Step

Given that we know x=1 is part of the solution set,
we back-substitute it into one of the initial equations:
$x+y=5$
$1+y=5\quad/-1$
$y=4$
Confirm by substituting into the first equation:
$-2(1)+5(4)=18$

Published by
Pearson

ISBN 10:
013421742X

ISBN 13:
978-0-13421-742-0

4

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