There are 300 students in the upper grades of a certain university, accounting for exactly 40% of the total number of students in the school. It is known that the ratio of the number of students in the middle and lower grades is 12:13. How many students are there in the lower grades?
某高校高年级有学生300人，恰好占全校总人数的40%，已知中、低年级的人数的比是12：13，问低年级有多少人？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">300 / (2/5)</gadget>
<output>750</output>

<gadget id="calculator">750 - 300</gadget>
<output>450</output>

<gadget id="calculator">12 + 13</gadget>
<output>25</output>

<gadget id="calculator">13 / 25</gadget>
<output>13/25 = around 0.52</output>

<gadget id="calculator">450 * (13/25)</gadget>
<output>234</output>

<result>234</result>