#### Answer

$y=3$

#### Work Step by Step

$Given,$ $\sqrt (2y)$$=\sqrt (9-y)$
Squaring,we get:
$2y=9-y$
$3y=9$
$y=9\div3=3$
We need to check by putting the obtained value in the original equation :
$L.H.S=\sqrt(2X3) =\sqrt 6=\sqrt (9-3)=R.H.S$
Hence,$y=3$ is a valid solution