Answer:
Hours
Step-by-step explanation:
21a. One week is too long so using hours will help, but when doing a quick thing you can use seconds.
21b. (Sorry I can't see the question, so I can't answer that part.)
:)
3a to the power of 2 plus 5a minus 2
the value of x is 90 degrees and the the value of y is 180 degrees
