These Add and Subtract Fractions with Unlike Denominators Using Equivalent Fractions Organizers 1-3 allow students to practice the following common core standard: CCSS.Math.Content. 5. NF.A.1: 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. The organizers require a strong understanding of L.C.M. (lowest common multiple), equivalent fractions, improper fractions, mixed fractions, and simplifying fractions. These organizers combine numerous concepts and the complexity increases with each organizer. Enjoy the first one as a preview!