If the two values being subtracted are mixed fractions, it is often easier to turn them into improper fractions to perform the subtraction. This avoids any kind regrouping or borrowing from the minuend fraction if the numerator in the subtrahend is larger.
I have seen a lot of kids quickly pass off their 2’s, 5’s, and 10’s. These tables have an obvious pattern and are much easier to learn. Then there is a serious slow down as kids hit the 3’s, 4’s, and 6’s. By the time they get to the 7’s, 8’s, and 9’s they’ve decided that multiplication is way too hard, and math isn’t their thing.