\"\"

\

The given values are \"\".

\

Where \"\" is the first term and \"\" is the common difference.

\

The sum of an arithmetic series \"\".

\

\"\"                  (Substitute \"\")

\

Apply multiplication property of equality: a = b then \"\".

\

\"\"      (Multiply each side by 2)

\

\"\"               (Cancel common terms)

\

\"\"                     (Multiply: \"\")\"\"

\

Apply division property of equality: a = b then \"\".

\

\"\"               (Divide each side by 19)

\

\"\"                          (Cancel common terms)

\

\"\"                               (Divide: \"\")

\

Apply subtraction property of equality: a = b then \"\".

\

\"\"          (Subtract 103 from each side)

\

\"\"                                            (Subtract: \"\")\"\"

\

Substitute \"\", n = 19 and \"\" in \"\".

\

\"\"

\

\"\"           (Subtract: \"\")

\

\"\"                 (Multiply: \"\")

\

Apply multiplication property of equality: a = b then \"\".

\

\"\" (Multiply each side by \"\")

\

\"\"                 (Cancel common term)

\

\"\"                              (Multiply: \"\")\"\"

\

Apply subtraction property of equality: a = b then \"\".

\

\"\"              (Subtract 26 from each side)

\

\"\"                                         (Subtract: \"\")

\

Apply division property of equality: a = b then \"\".

\

\"\"                                    (Divide each side by 18)

\

\"\"                                           (Cancel common terms)

\

d = 5                                                (Divide: \"\")

\

The 1st term is \"\" and 2nd term is a + d = \"\",

\

3rd term is a + 2d = \"\".\"\"

\

The first three terms of the series is 13, 18, 23.