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: .

               (Multiply: )

                       (Subtract: )

Apply subtraction property of equality: a = b then .

           (Subtract 7 from each side)

                (Apply additive inverse property: )

                       (Apply additive identity property: )

                               (Subtract: )

Apply division property of equality: a = b then .

                          (Divide each side by 5)

                               (Cancel common terms)

                                 (Divide: )

Apply sum of an arithmetic series formula: .

         (Substitute )

                 (Add: )

                       (Multiply: )

                          (Divide: )

The sum of the arithmetic series is 1083.