4.NF.3a:
Number And Operations - Fractions
Build Fractions From Unit Fractions By Applying And Extending Previous Understandings Of Operations On Whole Numbers.
Understand addition and subtraction of fractions as joining and separating parts referring to the same whole.
5.NF.1:
Number And Operations - Fractions
Use Equivalent Fractions As A Strategy To Add And Subtract Fractions.
Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12. (In general, a/b + c/d = (ad + bc)/bd.)