Find the values of a and b that make the quadrilateral a parallelogram.

Step-by-step explanation:
both halves of a diagonal must be equal.
so,
8b - 30 = 6b + 6
2b = 36
b = 18
and
9a - 13 = 5a + 5
4a = 18
a = 18/4 = 4.5