A pen is 8 yuan, Xiao Ming buys two of the same pen, and there is 4 yuan left, how much money does Xiao Ming have?
一支钢笔8元，小明买两支同样的钢笔，还剩4元，小明原来有多少钱？
<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<result>20</result>