Answer:
16. is 18 and 19. is 3750 and 21. is 894
Explanation:
I am sorry I was not able to answer all your questions correctly because some of them I was unaware of what the numbers were and I didn't know the formula to some of the shapes wait for more responses to be sure I really don't want to be the cause of you getting the answers wrong.
JUST TO BE SURE IS A PARALLELOGRAM'S FORMULA BH ?