There is a book, Xiaohua read 2 pages on the first day, and then read 2 more pages every day than the previous day, how many pages did he read on the 4th day?
有一本书，小华第一天看了2页，以后每一天都比前一天多看2页，第4天看了多少页？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">2 + 6</gadget>
<output>8</output>

<result>8</result>