A column of numbers is: 3, 7, 11, 15, 19... What is its 30th number?
一列数为：3、7、11、15、19…它的第30个数是多少．
<gadget id="calculator">30 - 1</gadget>
<output>29</output>

<gadget id="calculator">29 * 4</gadget>
<output>116</output>

<gadget id="calculator">3 + 116</gadget>
<output>119</output>

<result>119</result>