The ratio of science books to story books bought in the school library is 3:5, story books are 120 more than science books, how many books are bought in total?
学校图书室买来科技书和故事书的比是3：5，故事书比科技书多120本，两种书共买了多少本．
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(5/8) - (3/8)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">120 / (1/4)</gadget>
<output>480</output>

<result>480</result>