The incubation period of a chicken is generally 21 days, which is (7/10) that of a goose. How many days is the incubation period of a goose?
鸡的孵化期一般为21天，是鹅的孵化期的(7/10)，鹅的孵化期是多少天．
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">21 / (7/10)</gadget>
<output>30</output>

<result>30</result>