Algebra is only going to become more advanced as the years of school pass and if one has not gained full knowledge of it at its most basic level, it will be impossible to venture on. You have to algebra one step at a time. If you do these steps over and over, your brain will start to adjust and you will like it.
Subtracting fractions is similar to adding fractions. Most of the work involves the denominator. If the denominators of the two fractions are already the same, much of the work is done. Simply subtract the two numerators to get the answer fraction using the same denominator, and then reduce and make a proper fraction.