One of the hardest things to get across to children is how to add fractions. All too often they will just add the numerator (top number of the fraction) and denominator (bottom number of the fraction) and get the wrong answer. The key to success is to create two equivalent fractions with the same denominator. The denominator stays the same when adding the numerators.
Look at 2/3 + 5/9
It is not possible to add thirds and ninths directly, so the two fractions need to be converted to their lowest common denominator; in this case ninths. Don’t try to add fractions until children have a really good understanding of equivalent fractions.
2/3 is the same as 6/9 so the question now becomes:
6/9 + 5/9 which is easy: 6/9 + 5/9 = 11/9
Convert the 11/9 to a mixed number which is 1 and 2/9.
Done!