In fact, if you successfully learn a few algebra concepts then you will want to have more. Practice is really important in algebra and you ca not expect to learn everything from online courses or tutorials. You need to go through the concepts and the principles of algebra again and again in order to learn them.
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.