Answer
x = 121°
Explanation
Angle bottom left corner.
Since the triangle touches a horizontal plane, we know the 2 angles have to add up to 180 degrees.
115 + x = 180
x = 180-115 = 65°
Angle at the top
We know a full circle is 360 degrees.
Let’s say the triangle angle is x
x + 304 = 360
360 - 304 = 56°
Angle of triangle at the bottom right.
We know angles of a triangle add up to 180°.
Since we just calculated the 2 other triangles:
56° + 65° + x = 180
180 - 56 - 65 = 59°
As the triangle sits on a horizontal plane, the angle marked x in the picture + the interior angle have to add to 180.
59° + x = 180
x = 180 - 59 = 121°