Xiao Ming does 18 oral math problems per minute, Xiao Gang does twice as much as Xiao Ming, how many more oral math problems does Xiao Gang do per minute than Xiao Ming?
小明每分钟做18道口算题，小刚每分钟做的是小明的2倍，小刚每分钟比小明多做几道口算题？
<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">36 - 18</gadget>
<output>18</output>

<result>18</result>