There are 15 rows of lecture theaters in the school, the first row has 8 seats, and one seat is added every row after that. How many seats are there in this lecture theater?
学校阶梯教室共有15排，第一排8个座位，以后逐排增加一个座位，这个阶梯教室共有多少个座位．
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">14 * 1</gadget>
<output>14</output>

<gadget id="calculator">8 + 14</gadget>
<output>22</output>

<gadget id="calculator">8 + 22</gadget>
<output>30</output>

<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">30 * (15/2)</gadget>
<output>225</output>

<result>225</result>