The school buys a batch of books. There are 120 more literature and art books than science and technology books, and (4/9) of literature and art books is equal to (2/3) of science and technology books. How many books did you purchase in total?
学校购进一批图书，文艺书比科技书多120本，文艺书的(4/9)与科技书的(2/3)相等．共购进图书多少本？
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

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

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">120 / (1/5)</gadget>
<output>600</output>

<result>600</result>