The angle between radius and tangent to circle is 90 degrees.
The quadrilateral formed by the two tangents and the two rays has two angles of 90 degrees, an angle of 40 degrees and an unknown angle.
The sum of the angles of a quadrilateral is 360 degrees.
⇒ x = 360° - 90 - 90 - 40 = 140°
x = 140°