On Arbor Day, the students planted 12 rows of poplar trees and 8 rows of fir trees, a total of 300 trees. There are 15 fir trees in each row. How many poplar trees are there in each row?
植树节同学们植了12行杨树和8行杉树，一共是300棵，杉树每行有15棵，杨树每行有多少棵？
<gadget id="calculator">8 * 15</gadget>
<output>120</output>

<gadget id="calculator">300 - 120</gadget>
<output>180</output>

<gadget id="calculator">180 / 12</gadget>
<output>15</output>

<result>15</result>