A bookshelf has three layers: upper, middle, and lower. The upper layer contains 150 books, accounting for 2/5 of the total. The ratio of the middle layer to the lower layer is 5:4. Do you know how many books are placed in the lower layer?
一个书架有上中下三层，上层放了150本书，占总数的(2/5)，中层与下层的本数比是5：4，你知道下层放了多少本吗？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">150 / (2/5)</gadget>
<output>375</output>

<gadget id="calculator">375 - 150</gadget>
<output>225</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">225 / 9</gadget>
<output>25</output>

<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<result>100</result>