Question

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

Answer 1

Ok, when you subtract mixed numbers, you have to:
1/convert the numbers to fraction form
2/ if they don't have the same denominator, you must make them have the same denominator.
3/ calculating (subtract or add)
4/ regroup the answer
If you already have the same denominator, just subtract or add, skip steps 1, 2 and 4
for example:
\(5\dfrac{1}{6}-3\dfrac{1}{6}=2\dfrac{1}{6}\) treat \(\dfrac{1}{6}\) as a whole thing like "banana"