Question

What relationship exists between 12 years ago

Answer 1

They are supplementary, meaning that they add up to 180 degrees.

You can think of it like this:
The sum of a parallelogram's angles is 360 degrees.
Each pair of opposite angles are equivalent.
If you substitute m(<M) = m(<K) = a and m(<N) = m(<L) = b you would get
2*a + 2*b = 360
Divide by 2: a + b = 360
Therefore any consecutive angles(angles that are not opposite) add up to 180.