How can the composition of fractions facilitate operating with fractions?

Students add and subtract fractions with common denominators.

Fractions with common denominators can be composed or decomposed to model the change in a quantity of unit fractions.

Addition and subtraction of fractions with common denominators does not change the unit fraction from which they are composed.

Fractions greater than one can be added or subtracted as mixed numbers or improper fractions.

Fractions with common denominators are multiples of the same unit fraction.

Properties for addition and subtraction of natural numbers apply to fractions.