To make 5 dinner rolls, 1/3 cup of flour is used

Divide.

1/3 / 5

Or multiply by the reciprocal of 5:

1/3 * 1/5 = 1/15

Therefore 1/15 cup of flour is used to make 1 dinner roll.

We can set up a proportion:

5/1/3 = x/5 2/3

Multiply 5 2/3 to both sides:

28 1/3 / 1/3 = x

85 = x

So 85 rolls can be made with 5 2/3 cups of flour.

Where are the functions?