There are 28 rows of seats in the cinema, the first row has 20 seats, each row has 2 more seats than the front row, and how many seats are there in the last row?
电影院共有28排座位，第一排有20个座位，以后每排都比前排多2个座位，最后一排有多少个座位．
<gadget id="calculator">28 - 1</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<gadget id="calculator">20 + 54</gadget>
<output>74</output>

<result>74</result>