Answer:
125
Explanation:
You can find the interior angle next to the angle with the value of 100, because a straight line has an angle of 180, so that angle would be 80. You can do the same with the interior angle next to 135, with that angle having a value of 45.
The interior angles of a triangle always have the sum of 180, so to get the last interior angle add 80+45 and then subtract that from 180. That angle would be 55.
To get Y take the value of the interior angle subtract 55 from 180, which would be 125.