In the MNPK rectangle, O is the intersection point of the diagonals, the angle MON = 40 degrees. find the angle MNK.

From the properties of the diagonals of a rectangle, it is known that the diagonals of the rectangle are equal and the intersection point is halved.
Consider a triangle MON, in it ON = OM by the property of diagonals, so this triangle is isosceles.
One of the properties of an isosceles triangle is the equality of the angles at the base of the triangle.
From all this we get:
Angle MNK = MNO = (180 – 40) / 2 = 70 °
Answer: Angle MNK 70 °.