Dear there's no y in this figure.
Here's your answer.
Angle A = 30?
Angle C = 100?
We know that exterior angle of a triangle is equal to the sum of interior opposite angle.
So, x + 30? = 100? (Angle A = 30? by verticle opposite angle)
100?- 30? = x
70? = x
Hope this help you.
Regards,