The arithmetic series is .

The nth term of an arithmetic sequence 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: .

                         (Product of two same signs is positive)

                           (Add: 16 + 6 = 22)

Apply subtraction property of equality: a = b then .

   (Subtract 22 from each side)

             (Apply additive inverse property: )

                   (Apply additive identity property: )

                           (Subtract: )

Apply division property of equality: a = b then .

                      (Divide each side by negative 6)

                              (Cancel common terms)

n = 12                                    (Divide: )

The sum of an arithmetic series .

Where is the first term and is the nth term.

                     (Substitute )

                          (Subtract: )

                                (Multiply: )

                                  (Divide: )

The sum of the arithmetic series is .