#### Answer

x=15

#### Work Step by Step

The two angles form a right angle.
Angle Addition Postulate
$3x+(4x-15)=90$
combine like terms
$7x-15=90$
add 15 to each side
$7x-15+15=90+15$
$7x=105$
divide each side by 7
$7x\div7=105\div7$
$x=15$

Published by
Prentice Hall

ISBN 10:
0133281159

ISBN 13:
978-0-13328-115-6

x=15

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