Which of the numbers 28 33 45 57 39 and 36 could be subtracted from 84 without regrouping? explain

If i'm not mistaken it would be 33. 

 84
-33

51

28 can be subtracted from 84 with regrouping. I know this because you take the 3 from 33 and subtract it from the 4 from 84 and get 1. Then you get the other 3 from 33 and subtract it from 8 and get 5. So your final answer is 51.

Then why is the question on here if you know the answer

5/8 beds for each square yard