\[a_{1} = 9;\ \ \ \ \ \ d = 9;\ \ a_{n} = 189:\]
\[189 = 9 + 9 \cdot (n - 1)\]
\[189 = 9 + 9n - 9\ \ \ \ \ \ |\ :9\]
\[n = 21.\]
\[S = \frac{9 + 189}{2} \cdot 21 = \frac{198}{2} \cdot 21 =\]
\[= 99 \cdot 21 = 2079.\]
\[Ответ:2079.\ \]