geometry unit 7 lesson 6 for

1] Square; Rectangle; Quadrilateral.

2] All rectangles are Quadrilaterals.

3] Arrange four equal length sides, so the diagonals are equal length also.

4] As per the Isosceles trapezoid.
Base angles are equal to each other and upper both angles are equal to each other too.
So,
20x+9 = 14x+15
20x-14x = 15-9
6x = 6
x = 1°

K = M = 29°

Sum of all angles of quadrilateral equal to 360°.

360-(29+29) = 360-58 = 302°

Sum of upper both equal angles is 302°.
One of them will be 302/2 = 151°

Answer will be 151°.