Question

When you subtract mixed numbers, how do you know when you need to regroup?

Answer 1

not sure what you mean
do you mean when you subtract
something like

2 1/4 - 1 3/4
thats is when the second fraction part is greater than the firs?

Answer 2

yea

Answer 3

right
one way to do it is first subtract the whole numbers

2 - 1 = 1

1/4 - 3/4 = -1/2

now add these 2 results

1 + (-1/2) = 1/2

Answer 4

another way is to change the mixed numbers to improper (top heavy fractions) first