In the school group gymnastics performance, there are 300 boys and 240 girls, and 20 people stand in each row. How many rows are girls standing less than boys?
在学校团体操表演中，男生有300人，女生有240人，每行站20人，女生比男生少站多少行？
<gadget id="calculator">300 / 20</gadget>
<output>15</output>

<gadget id="calculator">240 / 20</gadget>
<output>12</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<result>3</result>