Understand a fraction a/b with a > 1 as a sum of fractions 1/b. In other words, any fraction is a sum of unit fractions.
4.NF.3.c
Add and subtract mixed numbers with like denominators, for example By replacing each mixed number with an equivalent fraction, and/or by using properties of operations and the relationship between addition and subtraction.
4.NF.3.d
Solve word problems involving addition and subtraction of fractions referring to the same whole and having like denominators.