Which of the numbers: 28,33,45,57,39,36 could be subtracted from 84 without regrouping? Explain.

I think it would be the one that has a ones place less than the one subtracting

because

24-11 is easy, 10+3

but 21-14 is harder

all of them have ones place that are bigger, except 33

33 would be the answer

33 because 3 is less than 8 and 3 is less than 4.