Two sides of a parallelogram are 30 and 20. One diagonal has a length of 40. What is the length of the other diagonal?
This will explain better than I can:
I'm almost certain this is a parallelogram. I can't visualize a way to assume it's a parallelogram and then change one of the unlabeled sides of the quadrilateral without breaking some of the given parameters. (bisection, lengths = 7, etc.)