∠MJK = 90 (It is a rectangle, so all its corners are right angles)
∠MJL = 90 - 27 = 63 (Complementary angles)
∠JLK = 180 - 90 = 27 = 63 (Sum of all angles in a triangle is 180)
∠KML = 27 (Isosceles triangle)
∠MNL = 180 - 27 - 27 - 126 (Sum of all angles in a triangle is 180)