One pig can be exchanged for 2 sheep, one sheep can be exchanged for 9 chickens, and 3 pigs can be exchanged for how many chickens.
一头猪可以换2只羊，一只羊可以换9只鸡，3头猪可以换多少只鸡．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 * 9</gadget>
<output>54</output>

<result>54</result>