School organization queue training. If there are 18 people standing in each row, there are exactly 15 rows standing. How many rows can you stand if there are 9 people in each row? Solve with ratios.
学校组织队列训练．如果每行站18人，正好站15行．如果每行站9人，可以站多少行？用比例解．
<gadget id="calculator">15 * 18</gadget>
<output>270</output>

<gadget id="calculator">270 / 9</gadget>
<output>30</output>

<result>30</result>