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.
Learn one table at a time. Select one multiplication table to learn at a time. Start with the simple tables such as 2s, 10s, 5s, and 11s. By the time you learn the more difficult tables such as the 7s and 8s, you will already know several facts. Remember, 1 x 4 is the same as 4 x 1 so you only have to learn half of the multiplication table because the other half is just written the other way.