The arithmetic sequence is .

The nth term of an arithmetic sequence is .

Here = First term of the sequence, d = common difference.

The sequence three arithmetic means between 3 and 27.

                  (Substitute )

                 (Substitute )

                          (Subtract: )

Apply subtraction property of equality: a = b then .

               (Subtract 3 from each side)

Apply commutative property of addition: .

                           (Apply additive inverse property: )

                                 (Subtract: )

Apply division property of equality: a = b then .

                            (Divide each side by 6)

                                 (Cancel common term)

d = 4                                      (Divide: )

The arithmetic means are 7, 11, 15, 19 and 23.