Let each equal angle of given quadrilateral be x.
We know that, sum of all interior angles of a quadrilateral is 360°.
∴ x + x + x + 144° = 360°
3x + 144° = 360°
3x = 360° - 144°
3x = 216°
x = 72°
Hence each equal angle of the quadrilateral is of 72° measures.