Sum of inside angles of a polygon= 180º(n-2)
n=number of sides.
This polygon has 6 sides, the sum of all its angles would be=180º(6-2)=720
let´s:
xº=inside angle
xº=720º-sum of the others inside angles.
xº=720º-(75º+130º+120º+105º+145º)=720º-575º=145º
yº=180º-xº=180º-145º=35º
Answer: yº=35º