now in a kite, the ∡x and the angle on the opposite side are twins.
the sum of all interior angles in a polygon are 180(n - 2), n = number of sides.
so a kite is a quadrilateral, 4 sides, so its interior angles add up to 180( 4 - 2) = 360°.
we know one side is 26°, and the opposite side is 90°, so the slack is 360 - 26 - 90 = 244°.
so the twins will take half each of that, namely each one takes 244/2 = 122° = ∡x.