The school bought back 45 literature and art books and 45 science and technology books, each literature and art book was 7 yuan, and each science and technology book was 5 yuan. How much more is it to buy literature and art books than science and technology books?
学校买回文艺书和科技书各45本，每本文艺书7元，每本科技书5元．买文艺书比科技书多多少钱？
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">2 * 45</gadget>
<output>90</output>

<result>90</result>