There are 9 weekends in a certain month, which is (3/10) of the total number of days in this month. How many days are there in this month? (solution by equation)
某月双休日共有9天，是这个月总天数的(3/10)．这个月有多少天？(用方程解)
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">9 / (3/10)</gadget>
<output>30</output>

<result>30</result>