The school library originally had 5,400 literary and technical books, of which the scientific and technical books were 20% less than the literary and artistic books. Recently, a batch of scientific and technological books were bought. At this time, the ratio of the number of scientific and technical books to literary and artistic books was 9:10. How many science and technology books did the library buy?
学校图书馆原有文艺书和科技书共5400本，其中科技书比文艺书少20%，最近又买来一批科技书，这时科技书和文艺书的本数的比是9：10，图书馆买来科技书多少本？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) + 1</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">9 + 10</gadget>
<output>19</output>

<gadget id="calculator">10 / 19</gadget>
<output>10/19 = around 0.526316</output>

<gadget id="calculator">5_400 / (9/5) / (10/19)</gadget>
<output>5_700</output>

<gadget id="calculator">5_700 - 5_400</gadget>
<output>300</output>

<result>300</result>