The number of students in the art group of the school is the calligraphy group (4/5), and the ratio of the number of people in the art group to the number of people in the mathematics group is 3:5. There are 30 people in the calligraphy group, how many people are there in the mathematics group?
学校美术组的人数是书法组的(4/5)，美术组人数与数学组人数的比是3：5．书法组有30人，数学组有多少人？
<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">30 / (3/4)</gadget>
<output>40</output>

<result>40</result>