Explanation:
I didn't need the other angles, but right of the bat you can tell it's two right triangles back to back.
y has to be 90° , as you have noticed they already gave you 70° on the right side of the shape meaning if you were to add 90 which is why plus 70 what would that give you? 160.
the total interior for a triangles angles has to be 180°. if you do the math 180 - 160 you get the leftover 20° for x.
I suck at explaining stuff, hope this helps