From the given figure, find the value of x + y + z.

By exterior angle property, the sum of interior opposite angles is equal to the exterior angle.
Here, by exterior angle property, $\angle \mathrm{y}$  being an exterior angle will be the sum of opposite interior angles.
Then, $\angle \mathrm{y}=90°+30°=120°$
By straight angle property, the sum of angles on a straight line = 180^o
Then, $\angle \mathrm{z}+30°=180°$
$\angle \mathrm{z}=150°$
Also, $\angle \mathrm{x}+90°=180°$
$\angle \mathrm{x}=90°$

Therefore, $\mathrm{x}+\mathrm{y}+\mathrm{z}=90°+120°+150°=360°$