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.
When adding fractions without a common denominator, it is necessary to find a common denominator before adding the numerators. Find two equivalent fractions by determining the least common multiple of the two denominators and using that as the denominator for both fractions.