What is the number 912 in the arithmetic sequence 3, 12, 21, 30, 39, 48, ....
在等差数列3，12，21，30，39，48，…中912是第多少个数．
<gadget id="calculator">912 - 3</gadget>
<output>909</output>

<gadget id="calculator">909 / 9</gadget>
<output>101</output>

<gadget id="calculator">101 + 1</gadget>
<output>102</output>

<result>102</result>