The number of science and technology books in the library is 75% of that of literature and art books, and the number of science and technology books is 150 less than that of literature and art books. How many technical books are there?
图书馆科技书的本数是文艺书的75%，科技书比文艺书少150本．科技书有多少本．
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">150 / (1/4)</gadget>
<output>600</output>

<gadget id="calculator">600 - 150</gadget>
<output>450</output>

<result>450</result>