The value of x is 110° .
A quadrilateral with three known angles: 128°, 82°, and 40°.
To find the fourth angle (let's call it x), you can use the fact that the sum of
the interior angles of a quadrilateral is always 360 degrees.
So, if we sum the known angles:
128 +82 +40 =250
To find x, subtract the sum of the known angles from the total sum of angles in a quadrilateral:
360 −250 =110
Therefore, x=110, completing the quadrilateral's set of angles.