The school library purchased 300 story books, 50 more than the science books (2/5). How many technical books should I buy?
学校图书室购进300本故事书，比科技书的(2/5)多50本．购进科技书多少本？
<gadget id="calculator">300 - 50</gadget>
<output>250</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">250 / (2/5)</gadget>
<output>625</output>

<result>625</result>