A pencil case is 9 cm long and 3 cm wide, what is the circumference of the pencil case in cm?
一个文具盒长9厘米，宽3厘米，这个文具盒的周长多少厘米．
<gadget id="calculator">9 + 3</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>