The arithmetic series is .

Where is first term of the sequence and d is common difference.

Here ,

Common difference ,

So .

The nth term of an arithmetic sequence is .

            (Substitute )

Distribute terms using distributive property: .

                         (Add: 38 + 3 = 41)

Apply subtraction property of equality: a = b then .

        (Subtract 41 from each side)

                           (Subtract: )

Apply division property of equality: a = b then .

                      (Divide each side by negative 3)

                               (Cancel common terms)

                                    (Divide: )

Apply sum of an arithmetic series formula: .

                (Substitute )

                      (Add: 38 + 2 = 40)

                              (Multiply: )

The sum of the arithmetic series is 260.