13.) If ABCD is a parallelogram, find the measure of angle D?
B-C:
(9x - 1)
D-A:
(13x - 25)

Answer:
13x-25 = 9x-1
4x-25=-1
4x=24
x=6
9(6)-1 = 54-1 = 53
So, angle d is 180-53 or 127 degrees.
Let me know if this helps!