There are 420 roosters in a chicken farm, and the number of hens is less than that of roosters (2/7). How many hens are there? (answer in two ways)
一个养鸡场有公鸡420只，母鸡只数比公鸡少(2/7)，母鸡有多少只？(用两种方法解答)
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">420 * (2/7)</gadget>
<output>120</output>

<gadget id="calculator">420 - 120</gadget>
<output>300</output>

<result>300</result>