One cow can be exchanged for 6 pigs, 2 cows can be exchanged for 9 sheep, 3 sheep can be exchanged for 20 chickens, and one cow can be exchanged for how many chickens.
一头牛可换6头猪，2头牛可换9只羊，3只羊可换20只鸡，一头牛可换多少鸡．
<gadget id="calculator">9 / 3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">20 * (3/2)</gadget>
<output>30</output>

<result>30</result>