Answer
$XZ = 12$
$YZ= 12$
Work Step by Step
By the given Figure
$\angle Z=90^{\circ}$ given
$\angle X=45^{\circ}$ given
So remaining$ \angle Y=45^{\circ}$
now $XY= 12 \sqrt 2$ given
By Theorem 5.5.1/ (45-45-90 Theorem)
$XZ = 12$
$YZ= 12$