Suppose R = {1, 3, 5, 7, 9, 11, 13, 15, 17} and D = {3, 6, 9, 12, 15, 18, 21, 24, 27}. What is Rn D?

The intersection of two sets, denoted as R ∩ D, is the set containing the elements that are common to both sets R and D.

From the given sets:
R = {1, 3, 5, 7, 9, 11, 13, 15, 17}
D = {3, 6, 9, 12, 15, 18, 21, 24, 27}

The intersection of R and D is:
R ∩ D = {3, 9, 15}

Therefore, the set Rn D is {3, 9, 15}.